fix: convert jest.config.js to jest.config.mjs (ES module syntax)

Agent-Logs-Url: https://github.com/christianlouis/InboxConverge/sessions/6e25705d-50db-4b0c-969c-1be4cb3f1745

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/jest.config.mjs

@@ -1,4 +1,4 @@
-const nextJest = require('next/jest');
+import nextJest from 'next/jest.js';
 
 const createJestConfig = nextJest({
   dir: './',
@@ -19,4 +19,4 @@ const customJestConfig = {
   ],
 };
 
-module.exports = createJestConfig(customJestConfig);
+export default createJestConfig(customJestConfig);