Implement environment variable setup for frontend; create .env.production and .env.development files if they don't exist, and update API URLs in frontend components to use dynamic API_BASE_URL for improved configuration management.

frontend/src/views/Roles.vue

@@ -82,7 +82,7 @@ const { showModal, modalConfig, alert, confirm, onConfirm, onCancel } = useModal
 async function loadUsers() {
   try {
     loading.value = true
-    const response = await fetch('http://localhost:3010/api/roles/users', {
+    const response = await fetch('${API_URL}/roles/users', {
       headers: {
         'Authorization': `Bearer ${authStore.token}`
       }
@@ -133,7 +133,7 @@ async function demoteToUser(userId, userName) {
 async function updateRole(userId, newRole) {
   try {
     loading.value = true
-    const response = await fetch(`http://localhost:3010/api/roles/users/${userId}`, {
+    const response = await fetch(`${API_URL}/roles/users/${userId}`, {
       method: 'PUT',
       headers: {
         'Content-Type': 'application/json',