fix: resolve eslint warnings and error

Remove unused eslint-disable directives in BookingCreateModal and GDPR page. Rename isMobile to _isMobile to match allowed unused vars pattern.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/routes/admin/+page.svelte

@@ -68,7 +68,7 @@
 		settings: 'expanded'
 	});
 
-	let isMobile = $state(false);
+	let _isMobile = $state(false);
 
 	// =============== Lifted Data Fetching ===============
 	// Fetch shared data once at page level to avoid duplicate API calls
@@ -95,10 +95,10 @@
 		if (!browser) return;
 
 		const mql = window.matchMedia('(max-width: 767px)');
-		isMobile = mql.matches;
+		_isMobile = mql.matches;
 
 		function handleChange(e: MediaQueryListEvent) {
-			isMobile = e.matches;
+			_isMobile = e.matches;
 			for (const key in sectionState) {
 				sectionState[key as keyof typeof sectionState] = e.matches ? 'collapsed' : 'expanded';
 			}