Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/actions/admin-media.ts

@@ -13,8 +13,8 @@ export async function uploadMedia(formData: FormData): Promise<void> {
   await requireStaff();
   const file = formData.get("file") as File | null;
   if (!file || file.size === 0) return;
-  if (file.size > MAX_SIZE) throw new Error("File too large (max 5MB)");
-  if (!ALLOWED.includes(file.type)) throw new Error("Invalid file type");
+  if (file.size > MAX_SIZE) return;
+  if (!ALLOWED.includes(file.type)) return;
 
   const baseDir = path.resolve(process.cwd(), MEDIA_DIR);
   // eslint-disable-next-line security/detect-non-literal-fs-filename