fix: Samsung SAF library scan, Qobuz album cover, M4A metadata save and log improvements

- Fix M4A/ALAC scan silently failing on Samsung by adding proper fallback
  to scanFromFilename when ReadM4ATags fails (consistent with MP3/FLAC/Ogg)
- Propagate displayNameHint to all format scanners so fd numbers (214, 207)
  no longer appear as track names when /proc/self/fd/ paths are used
- Cache /proc/self/fd/ readability in Kotlin to skip failed attempts after
  first failure, reducing error log noise and improving scan speed on Samsung
- Fix Qobuz download returning wrong album cover when track exists on
  multiple albums by preferring req.CoverURL over API default
- Fix FFmpeg M4A metadata save failing with 'codec not currently supported
  in container' by forcing mp4 muxer instead of ipod when cover art present
- Clean up FLAC SAF temp file after metadata write-back (was leaking)
- Update LRC lyrics tag to credit Paxsenix API
- Remove log message truncation, defer to UI preview truncation instead

lib/services/ffmpeg_service.dart

@@ -1158,8 +1158,11 @@ class FFmpegService {
     // For M4A/MP4, cover art is mapped as a video stream and stored in the
     // 'covr' atom automatically by FFmpeg. The '-disposition attached_pic'
     // flag is only valid for Matroska/WebM containers and must NOT be used here.
+    // Force the mp4 muxer when cover art is present because the default ipod
+    // muxer (auto-selected for .m4a) does not register a codec tag for mjpeg,
+    // causing "codec not currently supported in container" on FFmpeg 8.0+.
     if (hasCover) {
-      cmdBuffer.write('-map 1:v -c:v copy ');
+      cmdBuffer.write('-map 1:v -c:v copy -f mp4 ');
     }
 
     cmdBuffer.write('-c:a copy ');