Add HuggingFace token setting for speaker detection

- Add "Speakers" tab in Settings with HF token input field
- Include step-by-step instructions for obtaining the token
- Pass hf_token from settings through Rust → Python pipeline → diarize
- Token can also be set via HF_TOKEN environment variable as fallback
- Move skip_diarization checkbox to Speakers tab

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

python/voice_to_notes/services/pipeline.py

@@ -60,6 +60,7 @@ class PipelineService:
         min_speakers: int | None = None,
         max_speakers: int | None = None,
         skip_diarization: bool = False,
+        hf_token: str | None = None,
     ) -> PipelineResult:
         """Run the full transcription + diarization pipeline.
 
@@ -123,6 +124,7 @@ class PipelineService:
                 num_speakers=num_speakers,
                 min_speakers=min_speakers,
                 max_speakers=max_speakers,
+                hf_token=hf_token,
             )
         except Exception as e:
             print(