Fix: Explicitly import models in database.py to ensure table creation on Render

backend/app/core/database.py

@@ -1,5 +1,6 @@
 """Database connection and session management."""
 from sqlmodel import SQLModel, create_engine, Session
+from app import models  # Ensure all models are loaded for metadata
 from typing import Generator
 
 from app.core.config import settings