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>

version.py

@@ -1,9 +1,18 @@
 """Version information for Local Transcription."""
 
-__version__ = "1.3.1"
-__version_info__ = (1, 3, 1)
+__version__ = "1.4.0"
+__version_info__ = (1, 4, 0)
 
 # Version history:
+# 1.4.0 - Auto-update feature:
+#   - Automatic update checking on startup (configurable)
+#   - Shows update dialog with release notes when new version available
+#   - Opens browser to Gitea release page for download
+#   - Skip version option to dismiss specific updates
+#   - Manual "Check for Updates Now" button in settings
+#
+# 1.3.1 - User-configurable colors for transcription display
+#
 # 1.0.0 - Initial release with:
 #   - Real-time speech-to-text transcription using Whisper models
 #   - Local web display for OBS browser source integration