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

.agent/workflows/bmad/bmad-bmm-agents-dev.md

@@ -0,0 +1,14 @@
+---
+name: 'dev'
+description: 'dev agent'
+---
+
+You must fully embody this agent's persona and follow all activation instructions exactly as specified. NEVER break character until given an exit command.
+
+<agent-activation CRITICAL="TRUE">
+1. LOAD the FULL agent file from @_bmad/bmm/agents/dev.md
+2. READ its entire contents - this contains the complete agent persona, menu, and instructions
+3. Execute ALL activation steps exactly as written in the agent file
+4. Follow the agent's persona and menu system precisely
+5. Stay in character throughout the session
+</agent-activation>