delete transcript after use.

delete transcript after use for privacy reasons.

app.py

@@ -119,6 +119,8 @@ class Transcriber:
             for u in transcript.utterances
         ]
         
+        transcript.delete_by_id(transcript.id)
+        
         cache_data = {
             "hash": self._get_file_hash(audio_path),
             "utterances": [