Add a lyrics-only service mode view with the sung line centred and auto-sized, and a free local faster-whisper script to transcribe saved songs

CLAUDE.md

@@ -91,6 +91,23 @@ JSON shapes mirror the Tauri Rust bridge exactly — don't change one side alone
   edit feed with view/restore, caption injection, JSON export, API examples.
   Disabled unless `ADMIN_PASSWORD` is set (Dokploy Environment tab; compose passes
   `${ADMIN_PASSWORD:-}`). Login is rate-limited per IP.
+- **Service mode → 🎵 Lyrics** (`data.settings.serviceLyrics`, `serviceLyricsAutoscroll`):
+  lyrics-only view; the sung line is centred, highlighted and sized to the
+  largest font that fits ONE row. Sizing is measured with a hidden real
+  `.sl-line` in TWO passes — Bricolage Grotesque has an optical-size axis, so
+  glyphs get relatively wider at small sizes and a single 100px measurement
+  over-fits on phones. Re-fit (in place, never rebuilding rows — that would
+  move the scroll position) on resize, `document.fonts` load, and +900 ms.
+  Lyrics-only and the 📺 video panel are mutually exclusive.
+- **Free batch transcription**: `scripts/lyrics/auto_lyrics.py` (faster-whisper
+  `large-v3-turbo` int8 on CPU, no API key/credits; venv at
+  `~/.local/share/lyrics-asr/.venv`). `--missing` uses `GET /api/admin/media`
+  (admin or token). Measured on the 16-core laptop: ~0.3–0.65× real time;
+  openai-whisper medium was ~2.5×. **`vad_filter` must stay False** — VAD calls
+  sung music non-speech and returns an empty transcript. Karaoke/minus-one
+  tracks have no vocals (reported "instrumental?"); their lyrics were read from
+  the on-screen text (frame sampling + OCR), not audio. ElevenLabs Scribe also
+  works but spends the TTS credit balance (free tier = 10k/month).
 - Offline: the last-seen notes per video are cached in localStorage
   (`ytpNotesCache`, 200 videos), so saved songs keep their lyrics offline.
 - **Toast cap bug (fixed with this feature):** `toast()` used