알림삭제 오류 수정

frontend/src/App.tsx

@@ -1927,7 +1927,7 @@ function App() {
         markets={monitoredMarkets}
         marketSubscriptions={liveStompSubscriptions}
         activeMarket={symbol}
-        enabled={formalLogin && monitoredMarkets.length > 0}
+        enabled={formalLogin && monitoredMarkets.length > 0 && appSettingsLoaded}
         popupEnabled={appDefaults.tradeAlertPopup ?? true}
         chartMarkersActive={menuPage === 'chart'}
         onMarkersChange={markers => {

frontend/src/hooks/useAppSettings.ts

@@ -79,6 +79,14 @@ export function getAppSettingsCache(): AppSettingsDto {
   return _cache ?? {};
 }
 
+/** 낙관적 캐시 패치 — _cache 가 null 일 때도 다음 로드 전까지 임시 보관 */
+export function patchAppSettingsCache(patch: Partial<AppSettingsDto>): void {
+  if (_cache !== null) {
+    Object.assign(_cache, patch);
+  }
+  // _cache 가 null 이면 현재 로드 중이므로 건너뜀 (로드 완료 후 DB 저장값으로 덮어씌워짐)
+}
+
 export function subscribeAppSettings(listener: AppSettingsListener): () => void {
   _listeners.add(listener);
   return () => _listeners.delete(listener);

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>)