feat: Complete admin panel implementation

- Add user management system with all CRUD operations
- Add promotion statistics dashboard with export
- Simplify Trading & Market settings UI
- Fix promotion schema (dates now optional)
- Add missing API endpoints and PATCH support
- Add comprehensive documentation
- Fix critical bugs (deletePromotion, duplicate endpoints)

All features tested and production-ready.

frontend/src/utils/axios.js

@@ -1,16 +1,16 @@
-import axios from 'axios'
-import { useAuthStore } from '@/stores/auth'
-import { useToast } from 'vue-toastification'
+import axios from "axios";
+import { useAuthStore } from "@/stores/auth";
+import { useToast } from "vue-toastification";
 
 // Create axios instance
 const axiosInstance = axios.create({
-  baseURL: import.meta.env.VITE_API_URL || '/api',
+  baseURL: import.meta.env.VITE_API_URL || "/api",
   timeout: 15000,
   withCredentials: true,
   headers: {
-    'Content-Type': 'application/json',
+    "Content-Type": "application/json",
   },
-})
+});
 
 // Request interceptor
 axiosInstance.interceptors.request.use(
@@ -20,83 +20,97 @@ axiosInstance.interceptors.request.use(
     // if (token) {
     //   config.headers.Authorization = `Bearer ${token}`
     // }
-    return config
+    return config;
   },
   (error) => {
-    return Promise.reject(error)
+    return Promise.reject(error);
   }
-)
+);
 
 // Response interceptor
 axiosInstance.interceptors.response.use(
   (response) => {
-    return response
+    return response;
   },
   async (error) => {
-    const toast = useToast()
-    const authStore = useAuthStore()
+    const toast = useToast();
+    const authStore = useAuthStore();
 
     if (error.response) {
-      const { status, data } = error.response
+      const { status, data } = error.response;
 
       switch (status) {
         case 401:
           // Unauthorized - token expired or invalid
-          if (data.code === 'TokenExpired') {
+          if (data.code === "TokenExpired") {
             // Try to refresh token
             try {
-              const refreshed = await authStore.refreshToken()
+              const refreshed = await authStore.refreshToken();
               if (refreshed) {
                 // Retry the original request
-                return axiosInstance.request(error.config)
+                return axiosInstance.request(error.config);
               }
             } catch (refreshError) {
               // Refresh failed, logout user
-              authStore.clearUser()
-              window.location.href = '/'
+              authStore.clearUser();
+              window.location.href = "/";
             }
           } else {
-            authStore.clearUser()
-            toast.error('Please login to continue')
+            authStore.clearUser();
+            toast.error("Please login to continue");
           }
-          break
+          break;
 
         case 403:
           // Forbidden
-          toast.error(data.message || 'Access denied')
-          break
+          toast.error(data.message || "Access denied");
+          break;
 
         case 404:
           // Not found
-          toast.error(data.message || 'Resource not found')
-          break
+          toast.error(data.message || "Resource not found");
+          break;
 
         case 429:
           // Too many requests
-          toast.error('Too many requests. Please slow down.')
-          break
+          toast.error("Too many requests. Please slow down.");
+          break;
 
         case 500:
           // Server error
-          toast.error('Server error. Please try again later.')
-          break
+          toast.error("Server error. Please try again later.");
+          break;
+
+        case 503:
+          // Service unavailable - maintenance mode
+          if (data.maintenance) {
+            // Only redirect if user is not admin
+            if (!authStore.isAdmin) {
+              window.location.href = "/maintenance";
+            }
+            // Don't show toast for maintenance, page will handle it
+            return Promise.reject(error);
+          } else {
+            toast.error("Service temporarily unavailable");
+          }
+          break;
 
         default:
           // Other errors
           if (data.message) {
-            toast.error(data.message)
+            toast.error(data.message);
           }
       }
     } else if (error.request) {
       // Request made but no response
-      toast.error('Network error. Please check your connection.')
+      toast.error("Network error. Please check your connection.");
     } else {
       // Something else happened
-      toast.error('An unexpected error occurred')
+      toast.error("An unexpected error occurred");
     }
 
-    return Promise.reject(error)
+    return Promise.reject(error);
   }
-)
+);
 
-export default axiosInstance
+export default axiosInstance;