Unify database schema: Resolve all User model conflicts and auth table incompatibilities

Major changes:
- Consolidate 3 different User models into single unified model (models/user.py)
- Use UUID primary keys throughout (matches existing database schema)
- Add comprehensive authentication fields while preserving existing data
- Remove duplicate User model from auth.py, keep APIKey/RefreshToken/TokenBlacklist
- Update all imports to use unified User model consistently
- Create database migration (002_add_auth_fields.sql) for safe schema upgrade
- Fix frontend User interface to handle UUID string IDs
- Add backward compatibility fields (name property, role field)
- Maintain relationships for authentication features (api_keys, refresh_tokens)

Schema conflicts resolved:
✅ Migration schema (UUID, 7 fields) + Basic model (Integer, 6 fields) + Auth model (Integer, 10 fields)
   → Unified model (UUID, 12 fields with full backward compatibility)
✅ Field inconsistencies (name vs full_name) resolved with compatibility property
✅ Database foreign key constraints updated for UUID relationships
✅ JWT token handling fixed for UUID user IDs

This completes the holistic database schema unification requested after quick
patching caused conflicts. All existing data preserved, full auth system functional.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/core/auth_deps.py

@@ -61,7 +61,7 @@ def get_current_active_user(
     db: Session = Depends(get_db),
 ) -> Dict[str, Any]:
     """Get current authenticated and active user."""
-    from app.models.auth import User
+    from app.models.user import User
     
     user = db.query(User).filter(User.id == user_context["user_id"]).first()
     if not user:

backend/app/core/init_db.py

@@ -5,19 +5,18 @@ Creates all tables and sets up initial data.
 
 import logging
 from sqlalchemy.orm import Session
-from app.core.database import engine, SessionLocal
-from app.models.auth import Base as AuthBase, User, API_SCOPES
-from app.models.auth import APIKey
+from app.core.database import engine, SessionLocal, Base
+from app.models.user import User
+from app.models.auth import API_SCOPES, APIKey
 
-# Import other model bases here as they're created
-# from app.models.workflows import Base as WorkflowsBase
-# from app.models.agents import Base as AgentsBase
+# Import all models to ensure they're registered with Base
+from app.models import user, auth, agent, project
 
 def create_tables():
     """Create all database tables."""
     try:
-        # Create auth tables
-        AuthBase.metadata.create_all(bind=engine)
+        # Create all tables using the unified Base
+        Base.metadata.create_all(bind=engine)
         
         # Add other model bases here
         # WorkflowsBase.metadata.create_all(bind=engine)

backend/app/core/security.py

@@ -224,8 +224,8 @@ class AuthManager:
                     raise AuthenticationError("Token has been revoked")
                 
                 # Get user information
-                user_id = int(payload.get("sub"))
-                from app.models.auth import User
+                user_id = payload.get("sub")  # UUID as string
+                from app.models.user import User
                 user = session.query(User).filter(User.id == user_id).first()
                 
                 if not user or not user.is_active:
@@ -279,7 +279,7 @@ def create_token_response(user_id: int, user_data: Dict[str, Any]) -> Dict[str,
 
 def get_password_hash(password: str) -> str:
     """Hash a password for storage."""
-    from app.models.auth import User
+    from app.models.user import User
     return User.hash_password(password)