fix: Update transcript fetching to use YouTubeTranscriptApi for fallback mechanism

gemini_transcript.py

@@ -265,7 +265,7 @@ class YouTubeTranscriptFetcher:
             transcript = self.api.fetch(self.video_id, languages=self.languages)
         except NoTranscriptFound:
             logger.info("[Tier 1] Requested languages %s not found. Finding first available transcript...", self.languages)
-            transcript_list = self.api.list_transcripts(self.video_id)
+            transcript_list = YouTubeTranscriptApi.list_transcripts(self.video_id)
             first_transcript = next(iter(transcript_list))
             logger.info("[Tier 1] Falling back to language: %s", first_transcript.language_code)
             transcript = first_transcript.fetch()