fix: unify theme system - fix theme switching persistence

- Unified localStorage key to 'theme-preference' across all components
- Fixed header.tsx using wrong localStorage key ('theme' instead of 'theme-preference')
- Added localStorage hybrid persistence for instant theme changes
- Removed router.refresh() which was causing stale data revert
- Replaced Blue theme with Sepia
- Consolidated auth() calls to prevent race conditions
- Updated UserSettingsData types to include all themes

keep-notes/lib/i18n/load-translations.ts

@@ -25,6 +25,14 @@ export interface Translations {
     rememberMe: string
     orContinueWith: string
   }
+  sidebar: {
+    notes: string
+    reminders: string
+    labels: string
+    editLabels: string
+    archive: string
+    trash: string
+  }
   notes: {
     title: string
     newNote: string