feat: Complete backend API setup with registration endpoint

- Added user registration endpoint (/api/v1/auth/register)
- Created MongoDB database connection module
- Fixed user models to match frontend signup form
- Exposed backend port 8000 for development
- Configured Vite proxy for API requests
- Successfully tested user registration flow

Backend is now fully functional with:
- MongoDB connection
- User registration with password hashing
- JWT token generation
- Proper error handling

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

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

oauth/backend/app/db/__init__.py

@@ -0,0 +1 @@
+# Database module