This fixes multiple issues with the tag sidebar and activity calendar:

1. Tag disappearing bug: When filtering by a tag, the sidebar now shows all tags instead of only the selected tag
2. Activity calendar filtering: Calendar now shows full activity history instead of filtered results
3. Auto-update on memo changes: Sidebar tags and calendar now update automatically when creating/editing memos without requiring manual page refresh

Technical changes:
- Modified useFilteredMemoStats to fetch unfiltered UserStats from backend API for Home/Profile pages
- Fixed key mismatch bug in userStore where stats were stored with inconsistent keys
- Added statsStateId update in fetchUserStats to trigger reactivity
- Updated MainLayout to pass appropriate userName based on page context
- Archived/Explore pages continue to compute from cached memos (correct behavior)

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>