Add server monitoring and database backup pages

New sidebar sections wired to the backend's new admin APIs:
- Monitoring: live request/error-rate/latency stats plus a recent-requests
  table, polling every 8s.
- Backups: create/list/download database backups (auth'd blob download
  since the endpoint requires a Bearer token, not a plain link).

src/components/Sidebar.tsx

@@ -2,7 +2,16 @@
 
 import Link from "next/link";
 import { usePathname, useRouter } from "next/navigation";
-import { LayoutGrid, ListTree, MessageCircleQuestion, LogOut, Heart, UserCheck } from "lucide-react";
+import {
+  LayoutGrid,
+  ListTree,
+  MessageCircleQuestion,
+  LogOut,
+  Heart,
+  UserCheck,
+  Activity,
+  Database,
+} from "lucide-react";
 import { cn } from "@/lib/utils";
 import { useAuth } from "@/lib/auth-context";
 
@@ -11,6 +20,8 @@ const navItems = [
   { href: "/users", label: "کاربران در انتظار تایید", icon: UserCheck },
   { href: "/categories", label: "دسته‌بندی‌ها و گزینه‌ها", icon: ListTree },
   { href: "/questions", label: "سوالات پروفایل", icon: MessageCircleQuestion },
+  { href: "/monitoring", label: "مانیتورینگ سرور", icon: Activity },
+  { href: "/backups", label: "بک‌آپ دیتابیس", icon: Database },
 ];
 
 export function Sidebar() {