refactor: integrate Alembic, restructure project, and clean up

- Add Alembic configuration (alembic.ini, env.py) for database migrations
- Remove legacy wheel.db and unnecessary __pycache__ files
- Delete models.py to separate SQLAlchemy and Pydantic concerns
- Restructure main.py to use modular API routers (user/admin)
- Introduce config backend for centralized settings management

backend/services/crud.py

@@ -0,0 +1,32 @@
+from sqlalchemy.orm import Session
+from models import Item
+import random
+
+def get_items(db: Session):
+    return db.query(Item).all()
+
+def create_item(db: Session, title: str):
+    item = Item(title=title)
+
+    db.add(item)
+    db.commit()
+    db.refresh(item)
+
+    return item
+
+def delete_item(db: Session, item_id: int):
+    item = db.query(Item).filter(Item.id == item_id).first()
+
+    if item:
+        db.delete(item)
+        db.commit()
+
+    return item
+
+def spin_wheel(db: Session):
+    items = db.query(Item).all()
+
+    if not items:
+        return None
+
+    return random.choice(items)