perf: skip ffmpeg transcode for PocketTTS streaming — use WAV directly

PocketTTS emits 16-bit PCM WAV (16 kHz mono). WAV is natively supported
on all browsers including iOS/macOS Safari, so the ffmpeg MP3 transcode
is unnecessary for the streaming path.

Using format=wav for PocketTTS voices eliminates the ffmpeg subprocess
startup delay (~200–400 ms) and a pipeline stage, giving lower latency
to first audio frame. Kokoro and CF AI continue using MP3 (they output
MP3 natively or via the OpenAI-compatible endpoint).

The runner (MinIO storage) is unaffected — it still stores MP3 for
space efficiency.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/messages/en.json

@@ -302,6 +302,24 @@
   "book_detail_range_queuing": "Queuing\u2026",
   "book_detail_scrape_range": "Scrape range",
   "book_detail_admin": "Admin",
+  "book_detail_admin_book_cover": "Book Cover",
+  "book_detail_admin_chapter_cover": "Chapter Cover",
+  "book_detail_admin_chapter_n": "Chapter #",
+  "book_detail_admin_description": "Description",
+  "book_detail_admin_chapter_names": "Chapter Names",
+  "book_detail_admin_audio_tts": "Audio TTS",
+  "book_detail_admin_voice": "Voice",
+  "book_detail_admin_generate": "Generate",
+  "book_detail_admin_save_cover": "Save Cover",
+  "book_detail_admin_saving": "Saving…",
+  "book_detail_admin_saved": "Saved",
+  "book_detail_admin_apply": "Apply",
+  "book_detail_admin_applying": "Applying…",
+  "book_detail_admin_applied": "Applied",
+  "book_detail_admin_discard": "Discard",
+  "book_detail_admin_enqueue_audio": "Enqueue Audio",
+  "book_detail_admin_cancel_audio": "Cancel",
+  "book_detail_admin_enqueued": "Enqueued {enqueued}, skipped {skipped}",
   "book_detail_scraping_progress": "Fetching the first 20 chapters. This page will refresh automatically.",
   "book_detail_scraping_home": "\u2190 Home",
   "book_detail_rescrape_book": "Rescrape book",

ui/messages/fr.json

@@ -302,6 +302,24 @@
   "book_detail_range_queuing": "En file d'attente…",
   "book_detail_scrape_range": "Plage d'extraction",
   "book_detail_admin": "Admin",
+  "book_detail_admin_book_cover": "Couverture du livre",
+  "book_detail_admin_chapter_cover": "Couverture du chapitre",
+  "book_detail_admin_chapter_n": "Chapitre n°",
+  "book_detail_admin_description": "Description",
+  "book_detail_admin_chapter_names": "Noms des chapitres",
+  "book_detail_admin_audio_tts": "Audio TTS",
+  "book_detail_admin_voice": "Voix",
+  "book_detail_admin_generate": "Générer",
+  "book_detail_admin_save_cover": "Enregistrer la couverture",
+  "book_detail_admin_saving": "Enregistrement…",
+  "book_detail_admin_saved": "Enregistré",
+  "book_detail_admin_apply": "Appliquer",
+  "book_detail_admin_applying": "Application…",
+  "book_detail_admin_applied": "Appliqué",
+  "book_detail_admin_discard": "Ignorer",
+  "book_detail_admin_enqueue_audio": "Mettre en file audio",
+  "book_detail_admin_cancel_audio": "Annuler",
+  "book_detail_admin_enqueued": "{enqueued} en file, {skipped} ignorés",
   "book_detail_scraping_progress": "Récupération des 20 premiers chapitres. Cette page sera actualisée automatiquement.",
   "book_detail_scraping_home": "← Accueil",
   "book_detail_rescrape_book": "Réextraire le livre",

ui/messages/id.json

@@ -302,6 +302,24 @@
   "book_detail_range_queuing": "Mengantri…",
   "book_detail_scrape_range": "Rentang scrape",
   "book_detail_admin": "Admin",
+  "book_detail_admin_book_cover": "Sampul Buku",
+  "book_detail_admin_chapter_cover": "Sampul Bab",
+  "book_detail_admin_chapter_n": "Bab #",
+  "book_detail_admin_description": "Deskripsi",
+  "book_detail_admin_chapter_names": "Nama Bab",
+  "book_detail_admin_audio_tts": "Audio TTS",
+  "book_detail_admin_voice": "Suara",
+  "book_detail_admin_generate": "Buat",
+  "book_detail_admin_save_cover": "Simpan Sampul",
+  "book_detail_admin_saving": "Menyimpan…",
+  "book_detail_admin_saved": "Tersimpan",
+  "book_detail_admin_apply": "Terapkan",
+  "book_detail_admin_applying": "Menerapkan…",
+  "book_detail_admin_applied": "Diterapkan",
+  "book_detail_admin_discard": "Buang",
+  "book_detail_admin_enqueue_audio": "Antre Audio",
+  "book_detail_admin_cancel_audio": "Batal",
+  "book_detail_admin_enqueued": "Diantre {enqueued}, dilewati {skipped}",
   "book_detail_scraping_progress": "Mengambil 20 bab pertama. Halaman ini akan dimuat ulang otomatis.",
   "book_detail_scraping_home": "← Beranda",
   "book_detail_rescrape_book": "Scrape ulang buku",

ui/messages/pt.json

@@ -302,6 +302,24 @@
   "book_detail_range_queuing": "Na fila…",
   "book_detail_scrape_range": "Intervalo de extração",
   "book_detail_admin": "Admin",
+  "book_detail_admin_book_cover": "Capa do Livro",
+  "book_detail_admin_chapter_cover": "Capa do Capítulo",
+  "book_detail_admin_chapter_n": "Capítulo nº",
+  "book_detail_admin_description": "Descrição",
+  "book_detail_admin_chapter_names": "Nomes dos Capítulos",
+  "book_detail_admin_audio_tts": "Áudio TTS",
+  "book_detail_admin_voice": "Voz",
+  "book_detail_admin_generate": "Gerar",
+  "book_detail_admin_save_cover": "Salvar Capa",
+  "book_detail_admin_saving": "Salvando…",
+  "book_detail_admin_saved": "Salvo",
+  "book_detail_admin_apply": "Aplicar",
+  "book_detail_admin_applying": "Aplicando…",
+  "book_detail_admin_applied": "Aplicado",
+  "book_detail_admin_discard": "Descartar",
+  "book_detail_admin_enqueue_audio": "Enfileirar Áudio",
+  "book_detail_admin_cancel_audio": "Cancelar",
+  "book_detail_admin_enqueued": "{enqueued} enfileirados, {skipped} ignorados",
   "book_detail_scraping_progress": "Buscando os primeiros 20 capítulos. Esta página será atualizada automaticamente.",
   "book_detail_scraping_home": "← Início",
   "book_detail_rescrape_book": "Reextrair livro",

ui/messages/ru.json

@@ -302,6 +302,24 @@
   "book_detail_range_queuing": "В очереди…",
   "book_detail_scrape_range": "Диапазон глав",
   "book_detail_admin": "Администрирование",
+  "book_detail_admin_book_cover": "Обложка книги",
+  "book_detail_admin_chapter_cover": "Обложка главы",
+  "book_detail_admin_chapter_n": "Глава №",
+  "book_detail_admin_description": "Описание",
+  "book_detail_admin_chapter_names": "Названия глав",
+  "book_detail_admin_audio_tts": "Аудио TTS",
+  "book_detail_admin_voice": "Голос",
+  "book_detail_admin_generate": "Сгенерировать",
+  "book_detail_admin_save_cover": "Сохранить обложку",
+  "book_detail_admin_saving": "Сохранение…",
+  "book_detail_admin_saved": "Сохранено",
+  "book_detail_admin_apply": "Применить",
+  "book_detail_admin_applying": "Применение…",
+  "book_detail_admin_applied": "Применено",
+  "book_detail_admin_discard": "Отменить",
+  "book_detail_admin_enqueue_audio": "Поставить в очередь",
+  "book_detail_admin_cancel_audio": "Отмена",
+  "book_detail_admin_enqueued": "В очереди {enqueued}, пропущено {skipped}",
   "book_detail_scraping_progress": "Загружаются первые 20 глав. Страница обновится автоматически.",
   "book_detail_scraping_home": "← На главную",
   "book_detail_rescrape_book": "Перепарсить книгу",