fix: satisfy next build ESLint in admin-api (unused param)

next build runs ESLint (stricter than tsc --noEmit), which failed on the
unused `type` param in fetchCategories with no-unused-vars, breaking the
frontend production build. Reference it via `void type;` while keeping
the signature for API compatibility.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/admin-api.ts

@@ -164,10 +164,11 @@ function flattenCategories(nodes: V2Category[]): AdminCategory[] {
 // ── Public API ────────────────────────────────────────────────────────────────
 
 export async function fetchCategories(
-  _type?: "video" | "image"
+  type?: "video" | "image"
 ): Promise<AdminCategory[]> {
-  // V2 categories have no video/image type; `_type` is accepted for API
+  // V2 categories have no video/image type; `type` is accepted for API
   // compatibility but the content service returns a single tree.
+  void type;
   const tree = await safeGet<V2Category[]>("/v1/categories");
   return tree ? flattenCategories(tree) : [];
 }