Add save progress UI and fix MMS errors

Show a progress bar during MP3 generation, update styles, and improve MMS error messaging.

server/tts_service.py

@@ -32,6 +32,10 @@ def _get_mms():
 def _text_to_wav_mms(text: str, wav_path: str) -> None:
     try:
         import torch
+    except Exception as exc:
+        raise RuntimeError("MMS TTS 사용을 위해 torch/numpy가 정상 설치되어야 합니다.") from exc
+
+    try:
         import soundfile as sf
     except Exception as exc:
         raise RuntimeError("MMS TTS 사용을 위해 soundfile 설치가 필요합니다.") from exc