feat(storage): migrate file storage from local disk to MinIO

Replace local filesystem-based image storage with MinIO S3-compatible
object storage. All upload, serve, delete, and list operations now use
the MinIO bucket defined in MINIO_* env vars.

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

src/lib/minio.ts

@@ -0,0 +1,12 @@
+import { Client } from "minio";
+
+const minioClient = new Client({
+  endPoint: process.env.MINIO_ENDPOINT!,
+  accessKey: process.env.MINIO_ACCESS_KEY!,
+  secretKey: process.env.MINIO_SECRET_KEY!,
+  useSSL: process.env.MINIO_USE_SSL === "true",
+});
+
+export const MINIO_BUCKET = process.env.MINIO_BUCKET!;
+
+export default minioClient;