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/views/AdminPage.vue

@@ -37,6 +37,21 @@
         </button>
       </div>
 
+      <!-- Users Tab -->
+      <div v-if="activeTab === 'users'">
+        <AdminUsersPanel />
+      </div>
+
+      <!-- Config Tab -->
+      <div v-if="activeTab === 'config'">
+        <AdminConfigPanel />
+      </div>
+
+      <!-- Debug Tab -->
+      <div v-if="activeTab === 'debug'">
+        <AdminDebugPanel />
+      </div>
+
       <!-- Dashboard Tab -->
       <div v-if="activeTab === 'dashboard'" class="space-y-6">
         <!-- Quick Stats -->
@@ -735,6 +750,9 @@ import { useRouter } from "vue-router";
 import { useAuthStore } from "../stores/auth";
 import { useToast } from "vue-toastification";
 import axios from "../utils/axios";
+import AdminUsersPanel from "../components/AdminUsersPanel.vue";
+import AdminConfigPanel from "../components/AdminConfigPanel.vue";
+import AdminDebugPanel from "../components/AdminDebugPanel.vue";
 import {
   Shield,
   RefreshCw,
@@ -819,9 +837,12 @@ const isSavingPrice = ref(false);
 // Tabs
 const tabs = [
   { id: "dashboard", label: "Dashboard", icon: BarChart3 },
+  { id: "users", label: "Users", icon: Users },
+  { id: "config", label: "Config", icon: Shield },
   { id: "financial", label: "Financial", icon: DollarSign },
   { id: "transactions", label: "Transactions", icon: Activity },
   { id: "items", label: "Items", icon: Box },
+  { id: "debug", label: "Debug", icon: Shield },
 ];
 
 // Games