Serve image bytes via the SDK's documented transform

The SDK returns a Node IncomingMessage, not a web ReadableStream. undici
accepts it (verified against the live bucket, 21882 bytes), but the cast
claimed a type it never had. transformToByteArray is the documented API;
buffering is fine with uploads capped at 10MB.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/app/minio-images/[...key]/route.ts

@@ -37,12 +37,20 @@ export async function GET(
     const object = await getImage(key)
     if (!object.Body) return new Response(null, { status: 404 })
 
-    return new Response(object.Body as unknown as ReadableStream, {
+    // The SDK hands back a Node IncomingMessage, not a web ReadableStream. undici
+    // happens to accept it, but transformToByteArray is the documented API and keeps
+    // the types honest. Buffering is fine here - uploads are capped at 10MB.
+    const bytes = await object.Body.transformToByteArray()
+    // Copy out to a plain ArrayBuffer: a Uint8Array view is not a valid BodyInit.
+    const body = bytes.buffer.slice(
+      bytes.byteOffset,
+      bytes.byteOffset + bytes.byteLength
+    ) as ArrayBuffer
+
+    return new Response(body, {
       headers: {
         "Content-Type": object.ContentType ?? "application/octet-stream",
-        ...(object.ContentLength
+        "Content-Length": String(bytes.byteLength),
-          ? { "Content-Length": String(object.ContentLength) }
-          : {}),
         // Keys embed a random UUID, so an object never changes under a given key.
         // `private` keeps it out of any shared cache now that it is session-gated.
         "Cache-Control": "private, max-age=31536000, immutable",