feat: API contenuti taggati

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/upload-rules.ts

@@ -0,0 +1,16 @@
+import { extname } from 'node:path';
+
+export const ALLOWED: Record<string, string> = {
+  '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg', '.png': 'image/png', '.webp': 'image/webp', '.gif': 'image/gif',
+};
+export const MAX_BYTES = 5 * 1024 * 1024;
+
+export function validateUploadFile(file: unknown):
+  | { ok: true; file: File; ext: string }
+  | { ok: false; error: string } {
+  if (!(file instanceof File)) return { ok: false, error: 'Nessun file.' };
+  const ext = extname(file.name).toLowerCase();
+  if (!ALLOWED[ext]) return { ok: false, error: 'Formato non consentito (jpg, png, webp, gif).' };
+  if (file.size > MAX_BYTES) return { ok: false, error: 'File troppo grande (max 5 MB).' };
+  return { ok: true, file, ext };
+}