feat(now-playing): OpenSubsonic playbackReport for live now-playing (#1080)

* feat(now-playing): adopt OpenSubsonic playbackReport for live now-playing

Drive a small playback state machine (starting → playing ↔ paused → stopped)
on the Subsonic-server channel when the server advertises the OpenSubsonic
`playbackReport` extension (Navidrome ≥ 0.62), giving `getNowPlaying` a real
transport state and an extrapolated position. Reports send `ignoreScrobble=true`
so play counts stay on the existing `scrobble.view` 50% path (no double count),
and the effective playback speed is included so the server extrapolates position
correctly with the speed feature on.

- New `playbackReportSession` FSM mirrors the existing `playListenSession`
  lifecycle hooks and is wired at the same player call sites (start / gapless
  switch / queue restore / resume / 15s heartbeat / pause / seek / stop / ended /
  error / app quit). Servers without the extension degrade to the unchanged
  legacy `scrobble.view?submission=false` presence call.
- Gated through the existing serverCapabilities framework: a new
  `FEATURE_PLAYBACK_REPORT` (auto, extension-detected). The OpenSubsonic
  extensions probe now stores the full advertised list once and serves both
  AudioMuse `sonicSimilarity` and `playbackReport` from it, without disturbing
  the legacy Instant Mix opt-in on pre-0.62 servers.
- Now Playing dropdown shows a live position bar and a paused indicator.
- reportPlayback uses the real request params (mediaId / mediaType / positionMs).

Tests: FSM transitions + gating + legacy fallback, capability resolution,
extension-list probe storage/decoupling. Full suite green; no Tauri-boundary
changes.

* feat(now-playing): glide the Live position bar between polls

Extrapolate the position of `playing` entries locally (elapsed × reported
playbackRate from the last 10 s poll) and re-render once a second, so the Live
progress bar advances smoothly instead of jumping on each refresh. Paused and
position-less entries stay frozen. A linear width transition matched to the tick
keeps the fill gliding. Only applies to clients that report a position via the
playbackReport extension.

* fix(now-playing): tighten Live timer layout and report resume immediately

Keep the progress-bar width stable without a wide empty gap before the
timer: reserve ~2ch inside the current-time span only (right-aligned), not
on the whole clock block. Report `playing` to the server as soon as
resume() runs, matching the immediate `paused` report on pause instead of
waiting for the Rust `audio:playing` event.

* docs: CHANGELOG and credits for playbackReport live now-playing (PR #1080)

src/config/settingsCredits.ts

@@ -163,6 +163,7 @@ const CONTRIBUTOR_ENTRIES = [
       'What\'s New: remote WHATS_NEW.md from release assets, dev workspace mode, Highlights vs changelog tabs (PR #1058)',
       'Local library index: multi-genre browse, filters, and counts via track_genre table and blocking backfill (PR #1059)',
       'Audio: lazy-open output stream, 60s idle release (#1071), cold-start paused restore with silent engine prepare (PR #1073)',
+      'OpenSubsonic playbackReport — live now-playing state, gliding position bar, and immediate pause/resume on Navidrome ≥0.62 (PR #1080)',
     ],
   },
   {