fix: sync reactive state with data prop using \$effect

Replaces bare \$state(data.x) initialisers (which only capture the
initial value) with \$state + \$effect pairs so that state stays in sync
whenever page data is invalidated or the URL changes. Affects all list
pages (searchValue) and all edit/detail pages (form fields).

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

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

@@ -18,6 +18,7 @@
   let deleteOpen = $state(false);
   let deleting = $state(false);
   let searchValue = $state(data.search ?? "");
+  $effect(() => { searchValue = data.search ?? ""; });
   let searchTimeout: ReturnType<typeof setTimeout>;
 
   function debounceSearch(value: string) {