fix: add response_model, tighten overrides type annotation, add uuid import

Code review fixes for feature flags endpoint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/auth.py

@@ -1,5 +1,6 @@
 import secrets
 import string
+import uuid
 from datetime import datetime, timezone, timedelta
 from typing import Annotated
 from fastapi import APIRouter, Depends, HTTPException, status, Request
@@ -721,7 +722,7 @@ async def verify_email(
     return {"message": "Email verified successfully"}
 
 
-@router.get("/me/feature-flags")
+@router.get("/me/feature-flags", response_model=dict[str, bool])
 async def get_my_feature_flags(
     current_user: Annotated[User, Depends(get_current_active_user)],
     db: Annotated[AsyncSession, Depends(get_db)],
@@ -755,7 +756,7 @@ async def get_my_feature_flags(
     )
     plan_defaults = {d.flag_id: d.enabled for d in defaults_result.scalars().all()}
 
-    overrides: dict = {}
+    overrides: dict[uuid.UUID, bool] = {}
     if current_user.account_id:
         overrides_result = await db.execute(
             select(AccountFeatureOverride).where(