test: standardize test imports across test suite

- Add consistent Bun test framework imports to all test files
- Remove duplicate import statements
- Ensure uniform import style for describe, expect, and test functions
- Simplify test file import configurations

__tests__/api/index.test.ts

@@ -1,3 +1,4 @@
+import { describe, expect, test } from "bun:test";
 import { jest, describe, it, expect, beforeEach, afterEach } from '@jest/globals';
 import express from 'express';
 import request from 'supertest';