refactor: move record/playback to dedicated page, restore test mode in settings

- New '录制回放' page with sidebar nav entry
- Recording: start/stop/auto, file list with play/export/delete
- Playback: visual bar indicator, opens dashboards to see replayed data
- Settings: restored dev tools section with test mode toggle

static/js/router.js

@@ -4,6 +4,7 @@ const Router = {
         dashboard: PageDashboard,
         scene: PageScene,
         debug: PageDebug,
+        record: PageRecord,
         settings: PageSettings,
     },
     _currentPage: 'home',