fix: quality switch not updating video playback

- Use qn-specific MPD filename (bili_dash_{qn}.mpd) so each quality
  produces a distinct URI that triggers react-native-video to reload
- Add key={resolvedUrl} on <Video> to force remount on source change

components/NativeVideoPlayer.tsx

@@ -57,6 +57,7 @@ export function NativeVideoPlayer({
     <View style={[styles.container, style]}>
       {resolvedUrl ? (
         <Video
+          key={resolvedUrl}
           ref={videoRef}
           source={isDash
             ? { uri: resolvedUrl, type: 'mpd', headers: BILIBILI_HEADERS }

utils/dash.ts

@@ -7,7 +7,7 @@ import type { PlayUrlResponse } from '../services/types';
  */
 export async function buildDashMpdUri(playData: PlayUrlResponse, qn: number): Promise<string> {
   const xml = buildMpdXml(playData, qn);
-  const path = `${FileSystem.cacheDirectory}bili_dash.mpd`;
+  const path = `${FileSystem.cacheDirectory}bili_dash_${qn}.mpd`;
   await FileSystem.writeAsStringAsync(path, xml, { encoding: FileSystem.EncodingType.UTF8 });
   return path;
 }