fix(player): redesign cleanup pass — sleeve, tonearm, AGC, dead code

Production-readiness pass before merging the Studio Reference redesign
to master.

Audio (backend):
- Reset AGC `_spectrum_ref` envelope on `start()` so a long silent gap
  between sessions doesn't make the first new transients clip at the
  ceiling. Annotated the trade-off (loud transient lifts reference for
  a few seconds afterwards — the price of real loudness).
- Add `tests/test_audio_analyzer.py` with 10 cases: bin-edge layout,
  AGC attack/release asymmetry, lifecycle reset. Skips numpy-dependent
  cases when numpy isn't installed; CI has it.

Vinyl mode dead code removed:
- The toggle button was dropped during the sleeve refactor but the JS
  state, 2 s `setInterval`, `beforeunload` handler, and `applyVinylMode`
  call (commented out in app.js) all stayed. Now properly excised from
  player.js + app.js + window.* exports.
- Stripped the matching `.album-art-container.vinyl*` CSS block and its
  `vinylSpin` keyframes (~95 LoC).

Sleeve + tonearm fixes:
- Removed the duplicate `.now-playing .vinyl-stage` / `.vinyl-label` /
  `.tonearm` block that was overriding the new `.vinyl-stage` rules by
  source order — the uncommitted tonearm geometry never took effect
  because the stale clone won the cascade.
- Tightened tonearm to 36% × 36% at right:-6%, top:26% so the SVG
  bounding box stays right of the sleeve (sleeve right edge ~68%).
  Needle now lands on the visible disc grooves at both rest and
  playing rotations and never overlaps the cover.
- Removed sleeve `transform: rotate(-2.5deg)` + the matching mobile
  `-1.8deg` override; sleeve now sits flat and squared-off.
- Removed the 1px inset hairline on the sleeve and the 1px outline +
  inset highlight on the album art — cleaner, no semitransparent
  border noise.
- Album art inset 5% to expose a cardstock margin around the print
  (using explicit width/height — `inset` shorthand triggered the CSS
  replaced-element rule that uses the image's intrinsic size and blew
  out the grid track).

Mobile + misc:
- Removed mobile tonearm overrides at 720px and 420px — they were
  calibrated for the pre-sleeve geometry and put the needle back over
  the cover on phones; desktop geometry is proportional and works.
- Added `<meta name="mobile-web-app-capable">` alongside the legacy
  Apple variant to silence the deprecation warning in Chromium.
- Replaced the "PRIMARY" badge on display cards with a copper star
  icon (translation key still drives title + aria-label).
- `.gitattributes` with `* text=auto eol=lf` so Windows checkouts stop
  nagging "LF will be replaced by CRLF".

Annotations:
- "REF · 24" record-label catalogue mark marked as intentional non-i18n
  decoration in index.html.

CI: ruff clean, pytest 7 passed + 3 numpy-skipped (all 10 run on CI).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

media_server/static/js/app.js

@@ -21,7 +21,6 @@ import {
     activeTab, switchTab, updateTabIndicator, setMiniPlayerVisible,
     initTheme, toggleTheme, initAccentColor, applyAccentColor,
     renderAccentSwatches, selectAccentColor, toggleAccentPicker, lightenColor,
-    toggleVinylMode, applyVinylMode,
     visualizerEnabled, visualizerAvailable, setVisualizerEnabled,
     checkVisualizerAvailability, toggleVisualizer, applyVisualizerMode,
     loadAudioDevices, onAudioDeviceChanged,
@@ -96,8 +95,8 @@ Object.assign(window, {
     switchTab,
     // Theme & accent
     toggleTheme, toggleAccentPicker, selectAccentColor, lightenColor,
-    // Vinyl & visualizer
-    toggleVinylMode, toggleVisualizer,
+    // Visualizer (vinyl spin is structural CSS — no toggle)
+    toggleVisualizer,
     // Background
     toggleDynamicBackground,
     // Auth
@@ -163,9 +162,6 @@ window.addEventListener('DOMContentLoaded', async () => {
         navigator.serviceWorker.register('/sw.js').catch(() => {});
     }
 
-    // Vinyl is now structural / always-on via CSS — no init call needed.
-    // applyVinylMode();
-
     // Build the editorial spectrum bars. Fewer, fatter bars read better
     // than many thin ones at this column width. JS-managed so we can
     // drive heights from real audio data when available.