Fix display user not updating locally until app restart

Engines now read user.name from the config object at transcription time
instead of caching it at init, so name changes take effect immediately.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gui/main_window_qt.py

@@ -401,7 +401,6 @@ class MainWindow(QMainWindow):
             # Use Deepgram-based remote transcription
             self.transcription_engine = DeepgramTranscriptionEngine(
                 config=self.config,
-                user_name=user_name,
                 input_device_index=audio_device
             )
             self.transcription_engine.set_callbacks(
@@ -431,7 +430,7 @@ class MainWindow(QMainWindow):
                 initial_prompt=self.config.get('transcription.initial_prompt', ''),
                 no_log_file=self.config.get('transcription.no_log_file', True),
                 input_device_index=audio_device,
-                user_name=user_name
+                app_config=self.config
             )
 
         # Set up callbacks for transcription results