diff --git a/backend/Dockerfile b/backend/Dockerfile
index 62ff63d..49c736b 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -1,11 +1,13 @@
+
 FROM python:3.11-slim
 
 WORKDIR /app
 
-COPY requirements.txt .
+COPY requirements.txt ./
 RUN pip install --no-cache-dir -r requirements.txt
 
 COPY . .
 
-CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]
+EXPOSE 8000
 
+CMD [ "uvicorn", "backend.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload" ]
diff --git a/backend/crud.py b/backend/crud.py
index 21ddd4c..5b652a8 100644
--- a/backend/crud.py
+++ b/backend/crud.py
@@ -1,10 +1,11 @@
+
 from __future__ import annotations
-from typing import Iterable, List, Optional, Tuple
+from typing import List, Optional, Tuple
 from uuid import UUID as UUID_t
 from datetime import date
-import re, ast, operator
+import re, ast
 from sqlalchemy.orm import Session, joinedload
-import models
+from backend import models
 
 ALLOWED_NAMES = {"days", "nights"}
 ALLOWED_NODES = (
@@ -74,7 +75,7 @@ def generate_trip_items(
     trip: models.Trip,
     selected_tag_ids: List[UUID_t],
     marked_tag_ids: List[UUID_t],
-) -> Tuple[List[models.TripItem], List[UUID_t]]:
+) -> Tuple[List[UUID_t], List[UUID_t]]:
     """Regeneriert TripItems für einen Trip. Löscht alte, legt neue an.
     Gibt (created_ids, deleted_checked_ids) zurück."""
     # Sammle bestehende checked Items, falls sie verschwinden
@@ -94,12 +95,8 @@ def generate_trip_items(
 
     for it in items:
         item_tag_ids = {link.tag_id for link in it.tags}
-        # bestimmen, ob dupliziert werden soll
         intersection = item_tag_ids & marked_set
-        if marked_set and intersection:
-            per_tags = sorted(list(intersection))
-        else:
-            per_tags = [None]  # gemeinsames Item (oder keine marked match)
+        per_tags = sorted(list(intersection)) if (marked_set and intersection) else [None]
 
         for tag_id in per_tags:
             calc = render_name(it.name, trip.start_date, trip.end_date)
@@ -115,4 +112,4 @@ def generate_trip_items(
             created_ids.append(ti.id)
 
     db.flush()
-    return created_ids, deleted_checked
\ No newline at end of file
+    return created_ids, deleted_checked
diff --git a/backend/database.py b/backend/database.py
index 075e797..d718c8e 100644
--- a/backend/database.py
+++ b/backend/database.py
@@ -1,3 +1,4 @@
+
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker, declarative_base
 
@@ -7,12 +8,9 @@ engine = create_engine(DATABASE_URL, future=True)
 SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)
 Base = declarative_base()
 
-# FastAPI dependency
-from contextlib import contextmanager
-
 def get_db():
     db = SessionLocal()
     try:
         yield db
     finally:
-        db.close()
\ No newline at end of file
+        db.close()
diff --git a/backend/main.py b/backend/main.py
index 8a67dda..7ca6453 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -1,9 +1,8 @@
-from uuid import UUID
+
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
-from database import Base, engine
-from routes import items, tags, trips, trip_items, dev_seed
-
+from backend.database import Base, engine
+from backend.routes import items, tags, trips, trip_items, dev_seed
 
 # Create tables (for MVP without Alembic)
 Base.metadata.create_all(bind=engine)
@@ -22,4 +21,4 @@ app.include_router(tags.router)
 app.include_router(items.router)
 app.include_router(trips.router)
 app.include_router(trip_items.router)
-app.include_router(dev_seed.router)
\ No newline at end of file
+app.include_router(dev_seed.router)
diff --git a/backend/models.py b/backend/models.py
index a38d8e6..9cbf915 100644
--- a/backend/models.py
+++ b/backend/models.py
@@ -1,15 +1,12 @@
+
 import uuid
-from sqlalchemy import (
-    Column, String, Boolean, Date, ForeignKey, UniqueConstraint
-)
+from sqlalchemy import Column, String, Boolean, Date, ForeignKey, UniqueConstraint
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import relationship
-from database import Base
-
+from backend.database import Base
 
 class User(Base):
     __tablename__ = "users"
-
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     name = Column(String, nullable=False)
 
@@ -17,10 +14,8 @@ class User(Base):
     tags = relationship("Tag", back_populates="user", cascade="all, delete")
     trips = relationship("Trip", back_populates="user", cascade="all, delete")
 
-
 class Item(Base):
     __tablename__ = "items"
-
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     user_id = Column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=False)
     name = Column(String, nullable=False)  # z.B. "Zahnbürste" oder "{days} x Vitamin D3"
@@ -29,10 +24,9 @@ class Item(Base):
     tags = relationship("ItemTag", back_populates="item", cascade="all, delete")
     trip_items = relationship("TripItem", back_populates="item", cascade="all, delete")
 
-
 class Tag(Base):
     __tablename__ = "tags"
-    __table_args__ = (UniqueConstraint("user_id", "name"),)
+    __table_args__ = (UniqueConstraint("user_id", "name", name="uq_tag_user_name"),)
 
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     user_id = Column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=False)
@@ -44,20 +38,16 @@ class Tag(Base):
     trip_marked_tags = relationship("TripTagMarked", back_populates="tag", cascade="all, delete")
     trip_items = relationship("TripItem", back_populates="tag")
 
-
 class ItemTag(Base):
     __tablename__ = "item_tags"
-
     item_id = Column(UUID(as_uuid=True), ForeignKey("items.id", ondelete="CASCADE"), primary_key=True)
     tag_id = Column(UUID(as_uuid=True), ForeignKey("tags.id", ondelete="CASCADE"), primary_key=True)
 
     item = relationship("Item", back_populates="tags")
     tag = relationship("Tag", back_populates="items")
 
-
 class Trip(Base):
     __tablename__ = "trips"
-
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     user_id = Column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=False)
     name = Column(String)
@@ -69,36 +59,30 @@ class Trip(Base):
     marked_tags = relationship("TripTagMarked", back_populates="trip", cascade="all, delete")
     trip_items = relationship("TripItem", back_populates="trip", cascade="all, delete")
 
-
 class TripTagSelected(Base):
     __tablename__ = "trip_tag_selected"
-
     trip_id = Column(UUID(as_uuid=True), ForeignKey("trips.id", ondelete="CASCADE"), primary_key=True)
     tag_id = Column(UUID(as_uuid=True), ForeignKey("tags.id"), primary_key=True)
 
     trip = relationship("Trip", back_populates="selected_tags")
     tag = relationship("Tag", back_populates="trip_selected_tags")
 
-
 class TripTagMarked(Base):
     __tablename__ = "trip_tag_marked"
-
     trip_id = Column(UUID(as_uuid=True), ForeignKey("trips.id", ondelete="CASCADE"), primary_key=True)
     tag_id = Column(UUID(as_uuid=True), ForeignKey("tags.id"), primary_key=True)
 
     trip = relationship("Trip", back_populates="marked_tags")
     tag = relationship("Tag", back_populates="trip_marked_tags")
 
-
 class TripItem(Base):
     __tablename__ = "trip_items"
-
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     trip_id = Column(UUID(as_uuid=True), ForeignKey("trips.id", ondelete="CASCADE"), nullable=False)
     item_id = Column(UUID(as_uuid=True), ForeignKey("items.id"), nullable=False)
     name_calculated = Column(String, nullable=False)
     checked = Column(Boolean, nullable=False, default=False)
-    tag_id = Column(UUID(as_uuid=True), ForeignKey("tags.id"), nullable=True)
+    tag_id = Column(UUID(as_uuid=True), ForeignKey("tags.id"), nullable=True)  # null = gemeinsames Item
 
     trip = relationship("Trip", back_populates="trip_items")
     item = relationship("Item", back_populates="trip_items")
diff --git a/backend/requirements.txt b/backend/requirements.txt
index c30fe25..0712569 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -1,8 +1,6 @@
-fastapi
-uvicorn[standard]
-sqlalchemy
-asyncpg
-psycopg2-binary
-pydantic
-python-dotenv
 
+fastapi==0.115.0
+uvicorn==0.30.6
+SQLAlchemy==2.0.34
+psycopg2-binary==2.9.9
+pydantic==1.10.17
diff --git a/backend/routes/dev_seed.py b/backend/routes/dev_seed.py
index 7c860d6..c5cf6c6 100644
--- a/backend/routes/dev_seed.py
+++ b/backend/routes/dev_seed.py
@@ -1,63 +1,103 @@
+
 from fastapi import APIRouter, Depends
 from sqlalchemy.orm import Session
-import uuid
-from database import get_db
-import models
-
-FIXED_USER_ID = uuid.UUID("00000000-0000-0000-0000-000000000001")  # Fixed UUID for demo user
+from uuid import uuid4
+from datetime import date, timedelta
+from backend.database import get_db
+from backend import models
+from backend.crud import generate_trip_items
 
 router = APIRouter(tags=["dev"])
 
 @router.get("/dev/seed")
-def seed_data(db: Session = Depends(get_db)):
-    user_id = FIXED_USER_ID
 
-    # Create demo user if not exists
-    user = db.query(models.User).filter(models.User.id == user_id).first()
+def dev_seed(db: Session = Depends(get_db)):
+
+    # Create demo user
+    user = db.query(models.User).first()
     if not user:
-        user = models.User(id=user_id, name="Demo User")
+        user = models.User(id=uuid4(), name="Demo")
         db.add(user)
         db.flush()
 
     # Tags
-    tags = ["jari", "kristin", "felix", "auto", "sommer"]
-    tag_objs = []
-    for t in tags:
-        tag_obj = models.Tag(id=uuid.uuid4(), user_id=user_id, name=t)
-        db.add(tag_obj)
-        tag_objs.append(tag_obj)
+    tag_names = ["jari", "kristin", "felix", "auto", "sommer"]
+    name_to_tag = {}
+    for name in tag_names:
+        existing = db.query(models.Tag).filter(models.Tag.user_id==user.id, models.Tag.name==name).first()
+        if existing:
+            name_to_tag[name] = existing
+        else:
+            t = models.Tag(id=uuid4(), user_id=user.id, name=name)
+            db.add(t)
+            db.flush()
+            name_to_tag[name] = t
+
+    # Items (based on your original example)
+
+    items = [
+        ("Kinderwagen", ["jari"]),
+        ("Babyschale mit Sonnenschutz", ["jari", "auto"]),
+        ("Alle Schnuller", ["jari"]),
+        ("Sonnencreme", ["sommer"]),
+        ("Ladekabel Handy", []),
+        ("Ladekabel Mac", ["kristin"]),
+        ("Sonnenbrillen", ["sommer"]),
+        ("Schlafsack für {nights} Nächte", ["jari"]),
+        ("{days} x Vitamin D3", ["jari"]),
+        ("{days * 10} Windeln", ["jari"]),
+        ("{days} Unterhosen", ["felix", "kristin"]),
+        ("Badesachen", ["felix", "kristin"]),
+    ]
+
+    for name, tags in items:
+        existing = db.query(models.Item).filter(models.Item.user_id==user.id, models.Item.name==name).first()
+        if existing:
+            item = existing
+        else:
+            item = models.Item(id=uuid4(), user_id=user.id, name=name)
+            db.add(item)
+            db.flush()
+
+        # link tags
+        for tag_name in tags:
+            tag = name_to_tag[tag_name]
+            link = db.query(models.ItemTag).filter_by(item_id=item.id, tag_id=tag.id).first()
+            if not link:
+                db.add(models.ItemTag(item_id=item.id, tag_id=tag.id))
 
     db.flush()
 
-    # Items
-    items_data = [
-        ("Badesachen", ["sommer", "auto"]),
-        ("Sonnencreme", ["sommer"]),
-        ("Ladegerät", []),
-        ("Zelt", ["auto"]),
-        ("Schlafsack", []),
-        ("Strandspielzeug", ["sommer", "jari"]),
-    ]
-    for name, tag_names in items_data:
-        item = models.Item(id=uuid.uuid4(), user_id=user_id, name=name)
-        db.add(item)
-        db.flush()
-        for tag_name in tag_names:
-            tag_id = next(t.id for t in tag_objs if t.name == tag_name)
-            db.add(models.ItemTag(item_id=item.id, tag_id=tag_id))
-
-    selected_tags = [t for t in tag_objs if t.name in ["jari", "kristin", "auto", "sommer"]]
-    marked_tags = [t for t in tag_objs if t.name in ["kristin", "felix"]]
+    # Demo trip
     trip = models.Trip(
-        id=uuid.uuid4(),
-        user_id=user_id,
+        id=uuid4(),
+        user_id=user.id,
         name="Ostsee August 2025",
-        start_date="2025-08-01",
-        end_date="2025-08-14",
-        selected_tags=selected_tags,
-        marked_tags=marked_tags,
+        start_date=date(2025, 8, 18),
+        end_date=date(2025, 8, 20),
     )
     db.add(trip)
+    db.flush()
+
+    selected = [name_to_tag[n].id for n in ["jari", "felix", "kristin", "auto"]]
+    marked = [name_to_tag[n].id for n in ["kristin", "felix"]]
+
+    for tid in selected:
+        db.add(models.TripTagSelected(trip_id=trip.id, tag_id=tid))
+
+    for tid in marked:
+        db.add(models.TripTagMarked(trip_id=trip.id, tag_id=tid))
+
+    db.flush()
+
+    created_ids, _ = generate_trip_items(db, trip=trip, selected_tag_ids=selected, marked_tag_ids=marked)
 
     db.commit()
-    return {"message": "Seed data created", "user_id": str(user_id)}
+
+    return {
+        "user_id": str(user.id),
+        "trip_id": str(trip.id),
+        "selected_tag_ids": [str(x) for x in selected],
+        "marked_tag_ids": [str(x) for x in marked],
+        "created_trip_item_ids": [str(x) for x in created_ids],
+    }
\ No newline at end of file
diff --git a/backend/routes/items.py b/backend/routes/items.py
index d794944..971ba97 100644
--- a/backend/routes/items.py
+++ b/backend/routes/items.py
@@ -1,9 +1,10 @@
+
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.orm import Session, joinedload
 from uuid import UUID
-from database import get_db
-import models
-from schemas import ItemCreate, ItemOut
+from backend.database import get_db
+from backend import models
+from backend.schemas import ItemCreate, ItemOut
 
 router = APIRouter(prefix="/items", tags=["items"])
 
@@ -60,4 +61,4 @@ def delete_item(item_id: UUID, db: Session = Depends(get_db)):
     if not item:
         raise HTTPException(status_code=404, detail="Item not found")
     db.delete(item)
-    db.commit()
\ No newline at end of file
+    db.commit()
diff --git a/backend/routes/tags.py b/backend/routes/tags.py
index df516c3..70a4a74 100644
--- a/backend/routes/tags.py
+++ b/backend/routes/tags.py
@@ -1,14 +1,13 @@
+
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.orm import Session
 from uuid import UUID
-from database import get_db
-import models
-from schemas import TagCreate, TagOut
+from backend.database import get_db
+from backend import models
+from backend.schemas import TagCreate, TagOut
 
 router = APIRouter(prefix="/tags", tags=["tags"])
 
-FIXED_USER_ID = None  # will be created on seed; or set in your auth layer
-
 @router.get("/", response_model=list[TagOut])
 def list_tags(db: Session = Depends(get_db)):
     tags = db.query(models.Tag).all()
@@ -16,7 +15,6 @@ def list_tags(db: Session = Depends(get_db)):
 
 @router.post("/", response_model=TagOut)
 def create_tag(payload: TagCreate, db: Session = Depends(get_db)):
-    # For MVP: attach to first user (or create one)
     user = db.query(models.User).first()
     if not user:
         from uuid import uuid4
@@ -30,4 +28,4 @@ def create_tag(payload: TagCreate, db: Session = Depends(get_db)):
     db.add(tag)
     db.commit()
     db.refresh(tag)
-    return tag
\ No newline at end of file
+    return tag
diff --git a/backend/routes/trip_items.py b/backend/routes/trip_items.py
index 458fff2..9744033 100644
--- a/backend/routes/trip_items.py
+++ b/backend/routes/trip_items.py
@@ -1,9 +1,10 @@
+
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.orm import Session, joinedload
 from uuid import UUID
-from database import get_db
-import models
-from schemas import TripItemOut
+from backend.database import get_db
+from backend import models
+from backend.schemas import TripItemOut
 
 router = APIRouter(prefix="/trip-items", tags=["trip-items"])
 
@@ -48,4 +49,4 @@ def toggle_trip_item(trip_item_id: UUID, db: Session = Depends(get_db)):
         name_calculated=ti.name_calculated,
         checked=ti.checked,
         tag=ti.tag,
-    )
\ No newline at end of file
+    )
diff --git a/backend/routes/trips.py b/backend/routes/trips.py
index c6a85e8..f3c7fb1 100644
--- a/backend/routes/trips.py
+++ b/backend/routes/trips.py
@@ -1,10 +1,11 @@
+
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.orm import Session, joinedload
 from uuid import UUID
-from database import get_db
-import models
-from schemas import TripCreate, TripOut, TripUpdate, TripRegenerationResult
-from crud import generate_trip_items
+from backend.database import get_db
+from backend import models
+from backend.schemas import TripCreate, TripOut, TripUpdate, TripRegenerationResult
+from backend.crud import generate_trip_items
 
 router = APIRouter(prefix="/trips", tags=["trips"])
 
@@ -120,4 +121,4 @@ def reconfigure_trip(trip_id: UUID, payload: TripUpdate, db: Session = Depends(g
         "trip_id": trip.id,
         "deleted_checked_trip_item_ids": deleted_checked,
         "created_trip_item_ids": created_ids,
-    }
\ No newline at end of file
+    }
diff --git a/backend/schemas.py b/backend/schemas.py
index fa84222..76db648 100644
--- a/backend/schemas.py
+++ b/backend/schemas.py
@@ -1,3 +1,4 @@
+
 from typing import List, Optional
 from uuid import UUID
 from datetime import date
@@ -62,4 +63,4 @@ class TripItemOut(BaseModel):
 class TripRegenerationResult(BaseModel):
     trip_id: UUID
     deleted_checked_trip_item_ids: List[UUID] = []
-    created_trip_item_ids: List[UUID] = []
\ No newline at end of file
+    created_trip_item_ids: List[UUID] = []
diff --git a/docker-compose.yml b/docker-compose.yml
index 6a90846..293b1c9 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,25 +1,27 @@
-version: "3.9"
 
+version: "3.9"
 services:
+  db:
+    image: postgres:15-alpine
+    environment:
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_USER: postgres
+      POSTGRES_DB: postgres
+    ports:
+      - "5432:5432"
+    volumes:
+      - db_data:/var/lib/postgresql/data
   backend:
-    build: ./backend
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    depends_on:
+      - db
     ports:
       - "8000:8000"
     volumes:
-      - ./backend:/app
+      - ./:/app
     environment:
-      - DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/packlist
-    depends_on:
-      - db
-
-  db:
-    image: postgres:15
-    environment:
-      POSTGRES_USER: postgres
-      POSTGRES_PASSWORD: postgres
-      POSTGRES_DB: packlist
-    volumes:
-      - db_data:/var/lib/postgresql/data
-
+      - PYTHONUNBUFFERED=1
 volumes:
   db_data: