feat(stats): add stats server, API endpoints, config, and Anki integration

- Hono HTTP server with 20+ REST endpoints for stats data
- Stats overlay BrowserWindow with toggle keybinding
- IPC channel definitions and preload bridge
- Stats config section (toggleKey, serverPort, autoStartServer, autoOpenBrowser)
- Config resolver for stats section
- AnkiConnect proxy endpoints (guiBrowse, notesInfo)
- Note ID passthrough in card mining callback chain
- Stats CLI command with autoOpenBrowser respect

src/core/services/mpv.ts

@@ -115,6 +115,7 @@ export interface MpvIpcClientEventMap {
   'subtitle-ass-change': { text: string };
   'subtitle-timing': { text: string; start: number; end: number };
   'time-pos-change': { time: number };
+  'duration-change': { duration: number };
   'pause-change': { paused: boolean };
   'secondary-subtitle-change': { text: string };
   'media-path-change': { path: string };
@@ -314,6 +315,9 @@ export class MpvIpcClient implements MpvClient {
       emitTimePosChange: (payload) => {
         this.emit('time-pos-change', payload);
       },
+      emitDurationChange: (payload) => {
+        this.emit('duration-change', payload);
+      },
       emitPauseChange: (payload) => {
         this.playbackPaused = payload.paused;
         this.emit('pause-change', payload);