알림삭제 오류 수정

frontend/src/utils/uiPreferencesDb.ts

@@ -3,9 +3,10 @@
  */
 import {
   getAppSettingsCache,
+  patchAppSettingsCache,
   subscribeAppSettings,
 } from '../hooks/useAppSettings';
-import { saveAppSettings, type AppSettingsDto } from './backendApi';
+import { saveAppSettings } from './backendApi';
 import {
   EMPTY_UI_PREFERENCES,
   UI_PREFERENCES_VERSION,
@@ -64,9 +65,7 @@ export function patchUiPreferences(patch: Partial<UiPreferences>, immediate = fa
   const next = deepMerge(current as Record<string, unknown>, patch as Record<string, unknown>) as UiPreferences;
   next.v = UI_PREFERENCES_VERSION;
 
-  const cache = getAppSettingsCache();
-  const merged: AppSettingsDto = { ...cache, uiPreferences: next };
-  Object.assign(cache, merged);
+  patchAppSettingsCache({ uiPreferences: next });
 
   pendingPatch = pendingPatch
     ? (deepMerge(pendingPatch as Record<string, unknown>, patch as Record<string, unknown>) as Partial<UiPreferences>)