- Add GeoStats feature for tracking access source geography
  - Backend: geo_stats.go with realtime/batch write modes
  - API: config, data, summary endpoints
  - Frontend: Leaflet map on Dashboard, settings in Settings page
  - i18n: Chinese and English translations

- Improve version management
  - Inject Version, GitCommit, BuildTime via ldflags
  - Display version info in settings API response
  - Remove hardcoded version, use 'dev' as default