BREAKING CHANGE: Removed DeleteMemoTag and RenameMemoTag API endpoints
for better API consistency. Tags should now be managed by updating memo
content directly via UpdateMemo endpoint.

Backend changes:
- Remove RenameMemoTag and DeleteMemoTag RPC methods from proto
- Remove backend implementations in memo_service.go
- Regenerate protocol buffers (Go, TypeScript, OpenAPI)

Frontend changes:
- Remove RenameTagDialog component
- Simplify TagsSection to remove rename/delete functionality
- Improve tag styling with active state highlighting
- Add smooth transitions and better hover interactions
- Polish TagTree component for consistency
- Tags now only support click-to-filter (no inline editing)

Style improvements:
- Active tags highlighted with primary color and font-medium
- Consistent hover states across flat and tree views
- Better spacing and visual hierarchy
- Improved empty state styling

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