Refactor app to speech-only transcription tool

Remove image generation, text-to-speech, and chat features.
Keep speech transcription with Whisper.cpp, model manager, and settings.
Support multiple audio formats (WAV, MP3, M4A, OGG, FLAC, WebM, AAC)
via ffmpeg transcoding. Single-call API: upload → transcribe → download
as txt/json/md.

app/frontend/index.html

@@ -7,7 +7,7 @@
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Outfit:wght@300;400;500;600;700&display=swap" rel="stylesheet">
-    <title>Uncensored AI Studio</title>
+    <title>Speech Transcriber</title>
   </head>
 
   <body>