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>

src-tauri/src/commands/transcribe.rs

@@ -52,6 +52,7 @@ pub fn run_pipeline(
     min_speakers: Option<u32>,
     max_speakers: Option<u32>,
     skip_diarization: Option<bool>,
+    hf_token: Option<String>,
 ) -> Result<Value, String> {
     let manager = sidecar();
     manager.ensure_running()?;
@@ -70,6 +71,7 @@ pub fn run_pipeline(
             "min_speakers": min_speakers,
             "max_speakers": max_speakers,
             "skip_diarization": skip_diarization.unwrap_or(false),
+            "hf_token": hf_token,
         }),
     );