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/layout/components/app-sidebar.tsx

@@ -11,6 +11,13 @@ import {
   CollapsibleTrigger,
 } from "@/shared/components/ui/collapsible"
 import { ScrollArea } from "@/shared/components/ui/scroll-area"
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from "@/shared/components/ui/select"
 import {
   Tooltip,
   TooltipContent,
@@ -19,6 +26,7 @@ import {
 } from "@/shared/components/ui/tooltip"
 import { cn } from "@/shared/lib/utils"
 import { usePermission } from "@/shared/hooks"
+import { UnreadMessageBadge } from "@/modules/messaging/components/unread-message-badge"
 import { useSidebar } from "./sidebar-provider"
 import { NAV_CONFIG, Role } from "../config/navigation"
 
@@ -27,21 +35,28 @@ interface AppSidebarProps {
 }
 
 export function AppSidebar({ mode }: AppSidebarProps) {
-  const { expanded, toggleSidebar, isMobile } = useSidebar()
+  const { expanded, toggleSidebar, isMobile, currentRole, setCurrentRole } = useSidebar()
   const pathname = usePathname()
-  const { permissions, hasRole } = usePermission()
+  const { permissions, roles, hasRole } = usePermission()
 
-  // Determine which role's nav config to use based on session roles
-  let currentRole: Role = "teacher"
-  if (hasRole("admin")) {
-    currentRole = "admin"
-  } else if (hasRole("student")) {
-    currentRole = "student"
-  } else if (hasRole("parent")) {
-    currentRole = "parent"
+  // 自动检测当前角色（优先级 admin > student > parent > teacher）
+  function detectAutoRole(): Role {
+    if (hasRole("admin")) return "admin"
+    if (hasRole("student")) return "student"
+    if (hasRole("parent")) return "parent"
+    return "teacher"
   }
 
-  const allNavItems = NAV_CONFIG[currentRole] ?? NAV_CONFIG.teacher ?? []
+  // 用户在 NAV_CONFIG 中实际可用的角色（过滤掉未配置的角色）
+  const availableRoles = roles.filter((r) => NAV_CONFIG[r] !== undefined)
+
+  // 如果 context 中有 currentRole 且用户拥有该角色，使用 currentRole；否则自动检测
+  const effectiveRole: Role =
+    currentRole !== null && availableRoles.includes(currentRole)
+      ? currentRole
+      : detectAutoRole()
+
+  const allNavItems = NAV_CONFIG[effectiveRole] ?? NAV_CONFIG.teacher ?? []
 
   // Filter nav items by permission
   const navItems = allNavItems.filter((item) => {
@@ -154,6 +169,7 @@ export function AppSidebar({ mode }: AppSidebarProps) {
                 >
                   <item.icon className="size-4" />
                   <span>{item.title}</span>
+                  {item.href === "/messages" ? <UnreadMessageBadge /> : null}
                 </Link>
               )
             })}
@@ -163,12 +179,26 @@ export function AppSidebar({ mode }: AppSidebarProps) {
 
       {/* Sidebar Footer */}
       <div className="p-4">
+        {availableRoles.length > 1 && (expanded || isMobile) && (
+          <div className="px-2 pb-2">
+            <Select value={effectiveRole} onValueChange={(v) => setCurrentRole(v as Role)}>
+              <SelectTrigger className="w-full">
+                <SelectValue placeholder="切换角色" />
+              </SelectTrigger>
+              <SelectContent>
+                {availableRoles.map((r) => (
+                  <SelectItem key={r} value={r}>{r}</SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          </div>
+        )}
         {!isMobile && (
-           <button 
+           <button
              onClick={toggleSidebar}
              className="hover:bg-sidebar-accent text-sidebar-foreground flex w-full items-center justify-center rounded-md border p-2 text-sm transition-colors"
            >
-              {expanded ? "Collapse" : <ChevronRight className="size-4" />}
+              {expanded ? "收起" : <ChevronRight className="size-4" />}
            </button>
         )}
       </div>

src/modules/layout/components/sidebar-provider.tsx

@@ -9,12 +9,15 @@ import {
   SheetTitle,
 } from "@/shared/components/ui/sheet"
 import { cn } from "@/shared/lib/utils"
+import type { Role } from "@/shared/types/permissions"
 
 type SidebarContextType = {
   expanded: boolean
   setExpanded: (expanded: boolean) => void
   isMobile: boolean
   toggleSidebar: () => void
+  currentRole: Role | null
+  setCurrentRole: (role: Role | null) => void
 }
 
 const SidebarContext = React.createContext<SidebarContextType | undefined>(
@@ -38,6 +41,8 @@ export function SidebarProvider({ children, sidebar }: SidebarProviderProps) {
   const [expanded, setExpanded] = React.useState(true)
   const [isMobile, setIsMobile] = React.useState(false)
   const [openMobile, setOpenMobile] = React.useState(false)
+  // null 表示自动检测（按现有优先级 admin > student > parent > teacher）
+  const [currentRole, setCurrentRole] = React.useState<Role | null>(null)
 
   React.useEffect(() => {
     const checkMobile = () => {
@@ -62,7 +67,7 @@ export function SidebarProvider({ children, sidebar }: SidebarProviderProps) {
 
   return (
     <SidebarContext.Provider
-      value={{ expanded, setExpanded, isMobile, toggleSidebar }}
+      value={{ expanded, setExpanded, isMobile, toggleSidebar, currentRole, setCurrentRole }}
     >
       <div className="flex h-screen overflow-hidden w-full flex-col md:flex-row bg-background">
         {/* Mobile Trigger & Sheet */}