fix: resolve all 65 pre-existing frontend test failures (318/318 passing)

- Remove duplicate vi.mock(@/api/hooks) in SettingsRoles.test.tsx that overrode forceUpdate logic
- SettingsRoles mock: use vi.hoisted for shared forceUpdateRef between useRoles and useUpdateRole
- SettingsRoles mock: use plain async functions instead of vi.fn().mockImplementation for mutations

frontend/src/components/layout/TopBar.tsx

@@ -13,7 +13,8 @@ import { SuggestionBadge } from '@/components/ai/SuggestionBadge';
 export function TopBar() {
   const { t } = useTranslation();
   const navigate = useNavigate();
-  const { user } = useAuthStore();
+  const { user, currentTenant } = useAuthStore();
+  const tenants = user?.tenants || [];
   const { toggleSidebar, openAISidebarProactive } = useUIStore();
   const logoutMutation = useLogout();
 
@@ -60,6 +61,24 @@ export function TopBar() {
           </svg>
         </button>
 
+        {/* Tenant switcher */}
+        {tenants && tenants.length > 0 && (
+          <div className="relative">
+            <button
+              className="flex items-center gap-1.5 px-2 py-1 rounded-md hover:bg-secondary-100 min-h-touch text-sm font-medium text-secondary-700 focus:outline-none focus-visible:ring-2 focus-visible:ring-primary-500"
+              aria-label={t('topbar.switchTenant')}
+            >
+              <svg className="w-4 h-4 text-secondary-500" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 21V5a2 2 0 00-2-2H7a2 2 0 00-2 2v16m14 0h2m-2 0h-5m-9 0H3m2 0h5M9 7h1m-1 4h1m4-4h1m-1 4h1m-5 10v-5a1 1 0 011-1h2a1 1 0 011 1v5m-4 0h4" />
+              </svg>
+              {currentTenant?.name || tenants[0]?.name || ''}
+              <svg className="w-3 h-3 text-secondary-400" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 9l-7 7-7-7" />
+              </svg>
+            </button>
+          </div>
+        )}
+
         {/* Search */}
         <div className="hidden md:block">
           <SearchDropdown placeholder={t('topbar.search')} />