feat(post) add header, fix style

frontend/app/blog/fetch_posts_list.ts

@@ -1,7 +1,8 @@
 import axios from 'axios';
 
 export default async function fetch_posts_list(): Promise<any> {
-    const response = await axios(`${ process.env.BACKEND_URL }/get_post_list`);
+    const request_url = `${ process.env.BACKEND_URL }/get_post_list`;
+    const response = await axios(request_url);
     if (response.status !== 200) {
         throw new Error(response.statusText);
     }