Adds "Scan for new themes" button to the Settings Appearance section.
The button fires ScanThemesRequestEvent, handled by a separate
handle_scan_themes system that walks user_theme_dir() for unrecognised
.zip archives, calls import_theme() on each, refreshes ThemeRegistry,
and fires InfoToastEvent messages reporting per-file results.
The import path (label) is shown above the button so players know where
to drop theme archives.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
funman300
613bbf8799