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

_bmad/_config/manifest.yaml

@@ -1,7 +1,7 @@
 installation:
-  version: 6.0.0-alpha.22
-  installDate: 2026-01-09T12:45:17.078Z
-  lastUpdated: 2026-01-09T12:45:17.078Z
+  version: 6.0.0-alpha.23
+  installDate: 2026-01-18T13:25:57.063Z
+  lastUpdated: 2026-01-18T13:25:57.063Z
 modules:
   - core
   - bmm
@@ -9,3 +9,4 @@ ides:
   - gemini
   - claude-code
   - github-copilot
+  - antigravity