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/modules/dashboard/components/admin-dashboard/admin-dashboard.tsx

@@ -1,14 +1,31 @@
 import type { ReactNode } from "react"
-import { Users, LayoutDashboard, BookOpen, FileText, ClipboardList, Library, Activity } from "lucide-react"
+import Link from "next/link"
+import {
+  Activity,
+  BookOpen,
+  CalendarCheck,
+  CalendarClock,
+  ClipboardList,
+  FileText,
+  FolderOpen,
+  LayoutDashboard,
+  Library,
+  Megaphone,
+  Upload,
+  Users,
+  ChevronRight,
+} from "lucide-react"
 
 import type { AdminDashboardData } from "@/modules/dashboard/types"
 import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
 import { StatCard } from "@/shared/components/ui/stat-card"
 import { PageHeader } from "@/shared/components/ui/page-header"
 import { Badge } from "@/shared/components/ui/badge"
+import { Button } from "@/shared/components/ui/button"
 import { EmptyState } from "@/shared/components/ui/empty-state"
 import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/shared/components/ui/table"
 import { formatDate } from "@/shared/lib/utils"
+import { UserGrowthChart } from "./user-growth-chart"
 
 export function AdminDashboardView({ data }: { data: AdminDashboardData }) {
   return (
@@ -18,6 +35,18 @@ export function AdminDashboardView({ data }: { data: AdminDashboardData }) {
         description="System overview across users, learning content, and activity."
         actions={
           <>
+            <Button asChild variant="outline" size="sm" className="gap-2">
+              <Link href="/admin/users/import">
+                <Upload className="h-4 w-4" />
+                Import Users
+              </Link>
+            </Button>
+            <Button asChild size="sm" className="gap-2">
+              <Link href="/admin/announcements">
+                <Megaphone className="h-4 w-4" />
+                New Announcement
+              </Link>
+            </Button>
             <Badge variant="outline" className="gap-2">
               <Activity className="h-4 w-4" />
               {data.activeSessionsCount} active sessions
@@ -37,6 +66,66 @@ export function AdminDashboardView({ data }: { data: AdminDashboardData }) {
         <StatCard title="To grade" value={data.homeworkSubmissionToGradeCount} icon={FileText} valueClassName="tabular-nums" />
       </div>
 
+      {/* 快捷操作 */}
+      <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
+        <QuickActionCard
+          href="/admin/users/import"
+          icon={Upload}
+          title="批量导入用户"
+          description="通过 Excel 批量创建用户账号"
+        />
+        <QuickActionCard
+          href="/admin/announcements"
+          icon={Megaphone}
+          title="发布公告"
+          description="向全校或指定年级/班级发布通知"
+        />
+        <QuickActionCard
+          href="/admin/scheduling/changes"
+          icon={CalendarClock}
+          title="审批课表变更"
+          description="审核教师提交的课表变更与代课申请"
+        />
+        <QuickActionCard
+          href="/admin/scheduling/auto"
+          icon={CalendarClock}
+          title="自动排课"
+          description="基于规则自动生成周课表"
+        />
+        <QuickActionCard
+          href="/admin/files"
+          icon={FolderOpen}
+          title="文件管理"
+          description="查看与管理系统中所有上传文件"
+        />
+        <QuickActionCard
+          href="/admin/attendance"
+          icon={CalendarCheck}
+          title="考勤总览"
+          description="查看全校所有班级的考勤记录"
+        />
+      </div>
+
+      {/* 趋势图表 */}
+      <div className="grid gap-6 lg:grid-cols-2">
+        <Card>
+          <CardHeader>
+            <CardTitle className="text-base">用户增长趋势（近30天）</CardTitle>
+          </CardHeader>
+          <CardContent>
+            <UserGrowthChart data={data.userGrowth} />
+          </CardContent>
+        </Card>
+        <Card>
+          <CardHeader>
+            <CardTitle className="text-base">作业提交趋势（近7天）</CardTitle>
+          </CardHeader>
+          <CardContent>
+            <UserGrowthChart data={data.homeworkTrend} />
+          </CardContent>
+        </Card>
+      </div>
+
       <div className="grid gap-6 lg:grid-cols-3">
         <Card className="lg:col-span-1">
           <CardHeader>
@@ -111,6 +200,14 @@ export function AdminDashboardView({ data }: { data: AdminDashboardData }) {
               </TableBody>
             </Table>
           )}
+          <div className="flex justify-end pt-4">
+            <Button asChild variant="ghost" size="sm">
+              <Link href="/admin/users">
+                查看全部用户
+                <ChevronRight className="ml-1 h-4 w-4" />
+              </Link>
+            </Button>
+          </div>
         </CardContent>
       </Card>
     </div>
@@ -136,3 +233,31 @@ function ContentRow({
     </div>
   )
 }
+
+function QuickActionCard({
+  href,
+  icon: Icon,
+  title,
+  description,
+}: {
+  href: string
+  icon: React.ComponentType<{ className?: string }>
+  title: string
+  description: string
+}) {
+  return (
+    <Link href={href}>
+      <Card className="transition-colors hover:border-primary/50 hover:bg-accent/50">
+        <CardContent className="flex items-center gap-4 pt-6">
+          <div className="flex h-12 w-12 shrink-0 items-center justify-center rounded-lg bg-primary/10">
+            <Icon className="h-6 w-6 text-primary" />
+          </div>
+          <div className="space-y-1">
+            <div className="font-medium">{title}</div>
+            <div className="text-sm text-muted-foreground">{description}</div>
+          </div>
+        </CardContent>
+      </Card>
+    </Link>
+  )
+}

src/modules/dashboard/components/admin-dashboard/user-growth-chart.tsx

@@ -0,0 +1,46 @@
+"use client"
+
+import {
+  LineChart,
+  Line,
+  XAxis,
+  YAxis,
+  CartesianGrid,
+  Tooltip,
+  ResponsiveContainer,
+} from "recharts"
+
+interface UserGrowthChartProps {
+  data: Array<{ date: string; count: number }>
+}
+
+export function UserGrowthChart({ data }: UserGrowthChartProps) {
+  return (
+    <ResponsiveContainer width="100%" height={240}>
+      <LineChart data={data} margin={{ top: 5, right: 30, left: 20, bottom: 5 }}>
+        <CartesianGrid strokeDasharray="3 3" className="stroke-muted" />
+        <XAxis
+          dataKey="date"
+          className="text-xs"
+          tick={{ fontSize: 12 }}
+        />
+        <YAxis className="text-xs" tick={{ fontSize: 12 }} />
+        <Tooltip
+          contentStyle={{
+            backgroundColor: "hsl(var(--background))",
+            border: "1px solid hsl(var(--border))",
+            borderRadius: "6px",
+          }}
+        />
+        <Line
+          type="monotone"
+          dataKey="count"
+          stroke="hsl(var(--primary))"
+          strokeWidth={2}
+          dot={{ fill: "hsl(var(--primary))", r: 3 }}
+          name="新增用户"
+        />
+      </LineChart>
+    </ResponsiveContainer>
+  )
+}

src/modules/dashboard/data-access.ts

@@ -43,5 +43,7 @@ export const getAdminDashboardData = cache(async (scope?: DataScope): Promise<Ad
     homeworkSubmissionCount: homeworkStats.homeworkSubmissionCount,
     homeworkSubmissionToGradeCount: homeworkStats.homeworkSubmissionToGradeCount,
     recentUsers: usersStats.recentUsers,
+    userGrowth: [],
+    homeworkTrend: [],
   }
 })

src/modules/dashboard/types.ts

@@ -29,6 +29,8 @@ export type AdminDashboardData = {
   homeworkSubmissionCount: number
   homeworkSubmissionToGradeCount: number
   recentUsers: AdminDashboardRecentUser[]
+  userGrowth: Array<{ date: string; count: number }>
+  homeworkTrend: Array<{ date: string; count: number }>
 }
 
 export type StudentTodayScheduleItem = {