Highlights:
- Collapsible sidebar navigation with semantic grouping
- URL-synced pagination across all list pages
- Mailbox tag system (CRUD, filtering, per-mailbox binding)
- Browser notification support for new emails
- Admin user quick-preview Sheet panel
- Mailbox message export (JSON/CSV)
- Interactive API Playground page
- System monitoring sparkline and uptime bar
- PWA offline support with service worker
- One-click Docker + Traefik deployment
- CLI subcommands (config-check, env-init, version)
- Structured API error codes