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/tests/setup.ts

@@ -0,0 +1,9 @@
+/**
+ * Vitest setup file
+ * This file is loaded before all tests
+ */
+
+import { beforeAll, afterAll } from 'vitest'
+
+// Global setup can be added here if needed
+// For now, we keep it minimal as each test suite has its own setup