Fix: Core feature failures — transcribe, save, and subtitle download

Description: The old code was reading the server response twice in three different places — once to check for errors and again to get the actual data. By the second read, the response stream was already consumed and empty, causing the app to silently fail. Additionally, the address of the ASR server was never configured in the HTML file, so the app had no URL to send the audio to.These issues were present across the transcription, save, and subtitle download features — making all three unreliable.

Impact: Users could upload audio and click "Transcribe to Text" but the transcription result would never appear on screen. Clicking "Save to Corpus Server" after transcription did nothing — the record was never saved and no feedback was given. Clicking "Subtitles → Download SRT/VTT" would fail silently or show a confusing error with no useful information.