fix(citycorners): declare searchQuery and searching as $state

Both variables were used with bind:value but not declared.
Svelte 5 requires bind targets to be declared with $state().

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

apps/citycorners/apps/web/src/routes/(app)/cities/[slug]/add/+page.svelte

@@ -27,6 +27,8 @@
 	let error = $state('');
 	let geocoding = $state(false);
 	let imageError = $state(false);
+	let searchQuery = $state('');
+	let searching = $state(false);
 
 	const categories = [
 		{ value: 'sight', labelKey: 'category.sight' },