Fix proxy — use arrayBuffer to preserve multipart boundary, fix double /api/ in transcribe URL

app/api/[...slug]/route.ts

@@ -2,20 +2,29 @@ import { NextRequest, NextResponse } from 'next/server';
 
 const API_BASE = process.env.API_URL || 'https://ai.aaronnelson.studio';
 
-async function handler(request: NextRequest, { params }: { params: Promise<{ slug: string[] }> }) {
+async function handler(
+  request: NextRequest,
+  { params }: { params: Promise<{ slug: string[] }> }
+) {
   const { slug } = await params;
   const path = '/' + slug.join('/');
   const url = `${API_BASE}${path}${request.nextUrl.search}`;
 
   const headers = new Headers();
+
+  // Forward content-type exactly (includes multipart boundary)
   const contentType = request.headers.get('content-type');
   if (contentType) headers.set('content-type', contentType);
+
+  // Forward session cookie
   const cookie = request.headers.get('cookie');
   if (cookie) headers.set('cookie', cookie);
 
-  const body = request.method !== 'GET' && request.method !== 'HEAD'
-    ? await request.blob()
-    : undefined;
+  // Forward body
+  let body: BodyInit | undefined;
+  if (request.method !== 'GET' && request.method !== 'HEAD') {
+    body = await request.arrayBuffer();
+  }
 
   const response = await fetch(url, {
     method: request.method,
@@ -26,7 +35,8 @@ async function handler(request: NextRequest, { params }: { params: Promise<{ slu
   const responseHeaders = new Headers();
   const setCookie = response.headers.get('set-cookie');
   if (setCookie) responseHeaders.set('set-cookie', setCookie);
-  responseHeaders.set('content-type', response.headers.get('content-type') || 'application/json');
+  const respContentType = response.headers.get('content-type');
+  if (respContentType) responseHeaders.set('content-type', respContentType);
 
   return new NextResponse(response.body, {
     status: response.status,