fix: configure frontend services for environment API URLs

frontend/src/services/game.js

@@ -1,3 +1,7 @@
+const API_URL = import.meta.env.VITE_API_URL || ''
+const BASE = `${API_URL}/api/game`
+
+
 function apiError(message, status) {
   const err = new Error(message)
   err.status = status
@@ -6,7 +10,7 @@ function apiError(message, status) {
 
 export async function myGainsApi() {
   const token = localStorage.getItem('token')
-  const res = await fetch('/api/game/my-gains', {
+  const res = await fetch(`${BASE}/my-gains`, {
     headers: { Authorization: `Bearer ${token}` },
   })
   const data = await res.json()
@@ -16,7 +20,7 @@ export async function myGainsApi() {
 
 export async function participateApi(code) {
   const token = localStorage.getItem('token')
-  const res = await fetch('/api/game/participate', {
+  const res = await fetch(`${BASE}/participate`, {
     method: 'POST',
     headers: {
       'Content-Type': 'application/json',