fix(audio): correctly parse iTunSMPB gapless info from older iTunes M4A files

M4A files store the iTunSMPB value behind a 16-byte binary 'data' atom
header. The previous parser took bytes directly after the ASCII key,
landing in the binary header and producing a corrupted parts array
(total_valid=348 instead of ~13M samples), which caused take_duration
to exhaust the source in ~8ms — silent no-playback.

Fix: search for the " 00000000 " sentinel within 128 bytes of the key
to locate the actual value string, falling back to the old offset for
ID3v2/MP3 files where no binary header exists.

Also patches symphonia-format-isomp4 (local crate under patches/) to:
- Tolerate SL descriptor predefined=0x01 (older iTunes M4A)
- Convert descriptor.unwrap() panic to a proper decode error
- Gracefully skip malformed trak atoms (e.g. MJPEG cover-art streams)
  instead of failing the entire probe

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -44,3 +44,11 @@ souvlaki = { version = "0.8", default-features = false, features = ["use_zbus"]
 discord-rich-presence = "0.2"
 url = "2"
 thread-priority = "1"
+
+[patch.crates-io]
+# Local patch for Symphonia's isomp4 demuxer:
+# - Fixes descriptor.unwrap() panic on malformed esds atoms (older iTunes M4A)
+# - Tolerates SL predefined=0x01 (null) used by some older iTunes-purchased files
+# - Gracefully skips malformed trak atoms (e.g. MJPEG cover-art streams) instead
+#   of failing the entire probe
+symphonia-format-isomp4 = { path = "patches/symphonia-format-isomp4" }