feat: add metadata provider filter to series page

- Add `metadata_provider` query param to series API endpoints (linked/unlinked/specific provider)
- Return `metadata_provider` field in series response
- Add metadata filter dropdown on series page with all provider options
- Show small provider icon badge on linked series cards
- LiveSearchForm now wraps filters on two rows when needed

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

apps/backoffice/app/components/LiveSearchForm.tsx

@@ -68,7 +68,7 @@ export function LiveSearchForm({ fields, basePath, debounceMs = 300 }: LiveSearc
         if (timerRef.current) clearTimeout(timerRef.current);
         router.replace(buildUrl() as any);
       }}
-      className="flex flex-col sm:flex-row gap-3 items-start sm:items-end"
+      className="flex flex-col sm:flex-row sm:flex-wrap gap-3 items-start sm:items-end"
     >
       {fields.map((field) =>
         field.type === "text" ? (