feat(audio): migrate Symphonia 0.5 -> 0.6 (#999)

* feat(audio): migrate Symphonia 0.5 -> 0.6

Port the audio + analysis pipeline to the Symphonia 0.6 API:
- bump symphonia to 0.6 and symphonia-adapter-libopus to 0.3; drop rodio's
  symphonia-all feature to avoid a duplicate symphonia-core 0.5
- remove the local symphonia-format-isomp4 0.5 patch and rely on upstream 0.6
- switch codec registries to register_enabled_codecs / make_audio_decoder with
  AudioCodecParameters + AudioDecoderOptions
- rework decode.rs SizedDecoder and analysis decode loops for the new
  AudioDecoder trait, GenericAudioBufferRef, Time/Timestamp newtypes, and
  next_packet() -> Result<Option<Packet>>

Streaming regression fixes:
- ProbeSeekGate hides seekability during probe for non-MP4 progressive streams
  so Symphonia 0.6's trailing-metadata scan no longer forces a full download
  before ranged FLAC/MP3/OGG playback can start
- guard the streaming probe() with a 20s timeout on a worker thread so a stalled
  ranged source (e.g. right after a server switch) can no longer hang playback
  start until a player restart; add probe start/done diagnostics

* docs(changelog): note Symphonia 0.6 migration and streaming fixes (#999)

Add CHANGELOG entries (Changed + Fixed) and a CONTRIBUTORS line for the
Symphonia 0.6 migration, ranged-stream start-latency fix, and probe timeout.

* test(audio): cover streaming probe path and ProbeSeekGate

Add unit tests for SizedDecoder::new_streaming (success + garbage) and
ProbeSeekGate (seekability toggle, byte_len, read/seek passthrough) to
restore decode.rs above the 70% hot-path coverage gate (67.3% -> 79.4%).

src/config/settingsCredits.ts

@@ -151,6 +151,7 @@ const CONTRIBUTOR_ENTRIES = [
       'Performance Probe: on-demand (ui) cover throughput alongside backfill (lib) cpm (PR #947)',
       'Performance Probe: throughput (analysis tpm, cover cpm) measured over a trailing 5s window so the rate reacts promptly instead of coasting on minute-long inertia (PR #948)',
       'Cover backfill: follow the smart local/public endpoint switch so off-LAN clients stop fetching covers from the unreachable local address (PR #952)',
+      'Audio: Symphonia 0.6 migration with libopus adapter 0.3; ranged-stream start latency fix (probe seek-gate) and a probe timeout so a stalled stream no longer hangs playback start (PR #999)',
     ],
   },
   {