Configure API proxy and update API endpoint usage.

Added a new `/api/` proxy configuration in the Nginx setup to forward requests to the backend service. Adjusted the frontend code to use the new `/api` endpoint, improving flexibility and enabling easier deployment.

frontend/nginx.conf

@@ -5,4 +5,16 @@ server {
     root /usr/share/nginx/html;
     try_files $uri /index.html;
   }
+
+  location /api/ {
+    proxy_pass http://backend:8080/;
+    proxy_http_version 1.1;
+
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+
+    proxy_cookie_path / "/; SameSite=Lax";
+  }
 }

frontend/src/App.jsx

@@ -1,6 +1,6 @@
 import React, { useEffect, useState } from "react";
 
-const API = "http://localhost:8080";
+const API = "/api";
 
 async function api(path, opts = {}) {
   const res = await fetch(API + path, {