Fix TokenResponse schema: make user field non-optional and properly typed

- Changed user field from Optional[User] to required User type
- Ensures user object is always included in login response
- Pydantic now properly serializes the complete user object
- Frontend can now successfully retrieve response.user for localStorage

backend/schemas/users.py

@@ -42,4 +42,8 @@ class TokenResponse(BaseModel):
     user_id: int
     username: str
     role: str
-    user: Optional['User'] = None  # For frontend compatibility
+    user: User  # User object for frontend compatibility
+
+
+# Rebuild TokenResponse to resolve forward references
+TokenResponse.model_rebuild()