fix: reduce three-dot menu dots to match other icon sizes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/GroupsOverlay.tsx

@@ -444,9 +444,9 @@ function GroupControls({ groupId, zoom }: GroupControlsProps) {
               className="w-6 h-6 rounded-md flex flex-col items-center justify-center gap-[2px] hover:bg-white/20 transition-colors"
               title="Group options"
             >
-              <div className="w-1 h-1 rounded-full bg-white/70" />
-              <div className="w-1 h-1 rounded-full bg-white/70" />
-              <div className="w-1 h-1 rounded-full bg-white/70" />
+              <div className="w-[3px] h-[3px] rounded-full bg-white/70" />
+              <div className="w-[3px] h-[3px] rounded-full bg-white/70" />
+              <div className="w-[3px] h-[3px] rounded-full bg-white/70" />
             </button>
           </div>
         </div>