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/test-results/.last-run.json

@@ -1,9 +1,4 @@
 {
   "status": "failed",
-  "failedTests": [
-    "0e82f3542f319872cf04-73b68b8bffd834564925",
-    "0e82f3542f319872cf04-17c5a515b5b4a118f4fd",
-    "0e82f3542f319872cf04-6e4edab6f3b634b94a35",
-    "0e82f3542f319872cf04-121a19ba6e7e01eeb977"
-  ]
+  "failedTests": []
 }