refactor: Adjust chunk size to 4 MB and increase parallel uploads to 5

src/app/page.tsx

@@ -2,8 +2,8 @@
 
 import { useState, useEffect, useRef } from 'react';
 
-const CHUNK_SIZE = 8 * 1024 * 1024; // 8 MB
-const PARALLEL_UPLOADS = 4;
+const CHUNK_SIZE = 4 * 1024 * 1024; // 4 MB
+const PARALLEL_UPLOADS = 5;
 
 function bufferToBase64(buffer: ArrayBuffer) {
   let binary = '';