test(tags): replace 1 setTimeout sleep in TagTreeNode with vi.waitFor

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/routes/admin/tags/TagTreeNode.svelte.test.ts

@@ -164,8 +164,7 @@ describe('TagTreeNode', () => {
 			/einklappen|ausklappen/i.test(b.getAttribute('aria-label') ?? '')
 		) as HTMLButtonElement;
 		toggle?.click();
-		await new Promise((r) => setTimeout(r, 30));
-		// Map should have been mutated to opposite of current isCollapsed (false → true)
-		expect(map.get('tp1')).toBe(true);
+		// Map should have been mutated to opposite of current isCollapsed (false → true).
+		await vi.waitFor(() => expect(map.get('tp1')).toBe(true));
 	});
 });