feat(web): non-emoji group icons (inline SVG) for consistent cross-platform look

Group icons are semantic keys rendered as inline SVG (mirroring iOS SF Symbols /
Android Material) in the picker, group list and sidebar flags — instead of OS
emoji that vary per platform. Legacy emoji values still render as a fallback.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/js/version.js

@@ -1,2 +1,2 @@
 // Increment APP_VERSION with every code change
-export const APP_VERSION = 'v42';
+export const APP_VERSION = 'v43';