fix(captures): Play As autoplay + default voice + orphan recovery

- Hand /generate ids to the global SSE watcher so playback fires on completion. The mutation onSuccess was checking audio_path on a queued row, which is always empty — autoplay never ran.
- Bind the Play As voice selection to capture_settings.default_playback_voice_id, kept in sync with the Settings → Captures and Settings → MCP pickers. Picking from the split-button dropdown writes back to settings.
- Extract AudioBars from HistoryTable into a shared component; use it for the Play As generating state in place of Loader2.
- Stop the active-state hover from flashing white text when the button is in its lighter accent/10 fill.
- Drop the gradient avatar swatches from the Settings → Captures voice dropdown.
- Backend: when the gen worker exits without writing a terminal status (e.g. SQLite lock racing the failed-status write inside its own exception handler), the cancel endpoint now flips the row to failed instead of 409-ing. Worker also force-fails on its way out as a belt-and-suspenders.

app/src/i18n/locales/zh-TW/translation.json

@@ -29,7 +29,6 @@
     "snippetEmpty": "(無轉錄文字)",
     "noTranscriptError": "此擷取尚無轉錄文字",
     "captureCardLabel": "擷取 · {{when}}",
-    "playerVoiceLabel": "{{voice}} · {{captureId}}",
     "header": {
       "modelSummary": "Whisper {{stt}} · Qwen3 · {{llm}}"
     },