Add auto-update feature with Gitea release checking

- Add UpdateChecker class to query Gitea API for latest releases
- Show update dialog with release notes when new version available
- Open browser to release page for download (handles large files)
- Allow users to skip specific versions or defer updates
- Add "Check for Updates Now" button in settings
- Check automatically on startup (respects 24-hour interval)
- Pre-configured for repo.anhonesthost.net/streamer-tools

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/config.py

@@ -133,6 +133,15 @@ class Config:
                 'max_lines': 100,
                 'font_size': 12,
                 'theme': 'dark'
+            },
+            'updates': {
+                'auto_check': True,
+                'gitea_url': 'https://repo.anhonesthost.net',
+                'owner': 'streamer-tools',
+                'repo': 'local-transcription',
+                'skipped_versions': [],
+                'last_check': '',
+                'check_interval_hours': 24
             }
         }