lint: replace no-op flake8 script with gating ruff check, fix findings

backend/api/users.py

@@ -8,7 +8,6 @@ from typing import Annotated
 from fastapi import APIRouter, Depends, HTTPException, Query, Response, status
 from fastapi.responses import JSONResponse
 from sqlalchemy import text
-from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from backend.api.auth import get_current_user
@@ -19,16 +18,16 @@ from backend.constants.roles import (
     UserRole,
     is_admin_role,
 )
-from backend.db.session import get_auth_db, get_db
 from backend.db.models import Face, PhotoFavorite, PhotoPersonLinkage, User
+from backend.db.session import get_auth_db, get_db
 from backend.schemas.users import (
     UserCreateRequest,
     UserResponse,
-    UserUpdateRequest,
     UsersListResponse,
+    UserUpdateRequest,
 )
-from backend.utils.password import hash_password
 from backend.services.role_permissions import fetch_role_permissions_map
+from backend.utils.password import hash_password
 
 router = APIRouter(prefix="/users", tags=["users"])
 logger = logging.getLogger(__name__)
@@ -161,7 +160,7 @@ def get_current_admin_user(
     username = current_user["username"]
     
     # Check if any admin users exist
-    admin_count = db.query(User).filter(User.is_admin == True).count()
+    admin_count = db.query(User).filter(User.is_admin.is_(True)).count()
     
     # If no admins exist, allow current user to bootstrap as admin
     if admin_count == 0: