refactor(actions): extract clickOutside to shared module, replace 5 inline copies

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

frontend/src/lib/actions/clickOutside.ts

@@ -0,0 +1,15 @@
+export function clickOutside(node: HTMLElement): { destroy: () => void } {
+	function handleClick(event: MouseEvent) {
+		if (node && !node.contains(event.target as Node) && !event.defaultPrevented) {
+			node.dispatchEvent(new CustomEvent('clickoutside'));
+		}
+	}
+
+	document.addEventListener('click', handleClick, true);
+
+	return {
+		destroy() {
+			document.removeEventListener('click', handleClick, true);
+		}
+	};
+}