fix: chat — group creation (snake_case member_ids), readable mention color

src/components/chat/ChatWidget.tsx

@@ -115,7 +115,7 @@ function renderWithMentions(text: string, myName?: string) {
       const mentioned = part.slice(1).toLowerCase()
       const isMe = myFirst && mentioned.startsWith(myFirst)
       return (
-        <span key={i} className={cn('font-semibold', isMe ? 'bg-yellow-300/20 text-yellow-200 rounded px-0.5' : 'opacity-90')}>
+        <span key={i} className={cn('font-semibold rounded px-0.5', isMe ? 'bg-amber-100 text-amber-700 dark:bg-yellow-300/20 dark:text-yellow-300' : 'text-brand-600 dark:text-brand-300')}>
           {part}
         </span>
       )