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/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",