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/bmm/workflows/4-implementation/dev-story/instructions.xml

@@ -397,6 +397,7 @@
       - Verify all acceptance criteria are met
       - Ensure deployment readiness if applicable
       - Run `code-review` workflow for peer review
+      - Optional: Run TEA `*automate` to expand guardrail tests
     </action>
 
     <output>💡 **Tip:** For best results, run `code-review` using a **different** LLM than the one that implemented this story.</output>
@@ -406,4 +407,4 @@
     <action>Remain flexible - allow user to choose their own path or ask for other assistance</action>
   </step>
 
-</workflow>
+</workflow>