feat: add server-side pagination, search, and filtering to all collection and admin pages

- Public pages (videos, magazine, models): URL-driven search, sort, category/duration
  filters, and Prev/Next pagination (page size 24)
- Admin tables (videos, articles): search input, toggle filters, and pagination (page size 50)
- Tags page: tag filtering now done server-side via DB arrayContains query instead of
  fetching all items and filtering client-side
- Backend resolvers updated for videos, articles, models with paginated { items, total }
  responses and filter/sort/tag args

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

packages/frontend/src/routes/admin/articles/+page.server.ts

@@ -1,7 +1,19 @@
 import { adminListArticles } from "$lib/services";
 
-export async function load({ fetch, cookies }) {
+export async function load({ fetch, url, cookies }) {
   const token = cookies.get("session_token") || "";
-  const articles = await adminListArticles(fetch, token).catch(() => []);
-  return { articles };
+  const search = url.searchParams.get("search") || undefined;
+  const category = url.searchParams.get("category") || undefined;
+  const featuredParam = url.searchParams.get("featured");
+  const featured = featuredParam !== null ? featuredParam === "true" : undefined;
+  const offset = parseInt(url.searchParams.get("offset") || "0", 10);
+  const limit = 50;
+
+  const result = await adminListArticles(
+    { search, category, featured, limit, offset },
+    fetch,
+    token,
+  ).catch(() => ({ items: [], total: 0 }));
+
+  return { ...result, search, category, featured, offset, limit };
 }