feat(admin): 补全 admin 模块核心功能与产品体验优化

修复 v4 报告中的 13 个产品体验问题：新增用户管理列表页和系统设置页，重组导航菜单并补充缺失入口，增加角色切换机制，Dashboard 增加快捷操作和 recharts 趋势图表，考勤增加统计概览，排课增加课表网格视图，统一 Toast 操作反馈，同步更新架构文档

src/app/(dashboard)/admin/users/page.tsx

@@ -0,0 +1,48 @@
+import type { Metadata } from "next"
+import type { JSX } from "react"
+
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
+import { getSearchParam, type SearchParams } from "@/shared/lib/utils"
+import { getAdminUsers, getAdminUserRoles } from "@/modules/users/data-access"
+import { AdminUsersView } from "@/modules/users/components/admin-users-view"
+
+export const metadata: Metadata = {
+  title: "用户管理 - Next_Edu",
+  description: "管理系统所有用户",
+}
+
+export const dynamic = "force-dynamic"
+
+export default async function AdminUsersPage({
+  searchParams,
+}: {
+  searchParams: Promise<SearchParams>
+}): Promise<JSX.Element> {
+  await requirePermission(Permissions.USER_MANAGE)
+
+  const sp = await searchParams
+  const page = Number(getSearchParam(sp, "page") ?? "1") || 1
+  const search = getSearchParam(sp, "search") ?? ""
+  const role = getSearchParam(sp, "role") ?? ""
+
+  const [result, roleOptions] = await Promise.all([
+    getAdminUsers({ page, search: search || undefined, role: role || undefined }),
+    getAdminUserRoles(),
+  ])
+
+  return (
+    <div className="flex h-full flex-col space-y-6 p-8">
+      <AdminUsersView
+        users={result.items}
+        roleOptions={roleOptions}
+        page={result.page}
+        pageSize={result.pageSize}
+        total={result.total}
+        totalPages={result.totalPages}
+        search={search}
+        roleFilter={role}
+      />
+    </div>
+  )
+}