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/users/data-access.ts

@@ -1,7 +1,7 @@
 import "server-only"
 
 import { cache } from "react"
-import { and, count, desc, eq, gt, inArray } from "drizzle-orm"
+import { and, count, desc, eq, gt, ilike, inArray, or } from "drizzle-orm"
 
 import { auth } from "@/auth"
 import { db } from "@/shared/db"
@@ -304,3 +304,97 @@ export const getUserIdsByGradeId = cache(
     return rows.map((r) => r.id)
   }
 )
+
+/** Returns all user IDs (used for school-wide announcement notifications). */
+export const getAllUserIds = cache(async (): Promise<string[]> => {
+  const rows = await db.select({ id: users.id }).from(users)
+  return rows.map((r) => r.id)
+})
+
+export type AdminUserListItem = {
+  id: string
+  name: string | null
+  email: string
+  roles: string[]
+  phone: string | null
+  createdAt: Date
+}
+
+export type AdminUserListResult = {
+  items: AdminUserListItem[]
+  total: number
+  page: number
+  pageSize: number
+  totalPages: number
+}
+
+export async function getAdminUsers(params: {
+  page?: number
+  pageSize?: number
+  search?: string
+  role?: string
+}): Promise<AdminUserListResult> {
+  const page = Math.max(1, params.page ?? 1)
+  const pageSize = Math.min(100, Math.max(1, params.pageSize ?? 20))
+  const offset = (page - 1) * pageSize
+
+  const conditions = []
+  if (params.search) {
+    const search = `%${params.search}%`
+    conditions.push(
+      or(ilike(users.name, search), ilike(users.email, search))
+    )
+  }
+
+  const whereClause = conditions.length > 0 ? and(...conditions) : undefined
+
+  const [userRows, countRow] = await Promise.all([
+    db
+      .select()
+      .from(users)
+      .where(whereClause)
+      .orderBy(desc(users.createdAt))
+      .limit(pageSize)
+      .offset(offset),
+    db.select({ value: count() }).from(users).where(whereClause),
+  ])
+
+  const userIds = userRows.map((u) => u.id)
+  const roleRows = userIds.length
+    ? await db
+        .select({ userId: usersToRoles.userId, roleName: roles.name })
+        .from(usersToRoles)
+        .innerJoin(roles, eq(usersToRoles.roleId, roles.id))
+        .where(inArray(usersToRoles.userId, userIds))
+    : []
+
+  const rolesByUserId = new Map<string, string[]>()
+  for (const row of roleRows) {
+    const list = rolesByUserId.get(row.userId) ?? []
+    list.push(row.roleName)
+    rolesByUserId.set(row.userId, list)
+  }
+
+  const items = userRows.map((u) => ({
+    id: u.id,
+    name: u.name,
+    email: u.email,
+    roles: rolesByUserId.get(u.id) ?? [],
+    phone: u.phone,
+    createdAt: u.createdAt,
+  }))
+
+  const total = Number(countRow[0]?.value ?? 0)
+  return {
+    items,
+    total,
+    page,
+    pageSize,
+    totalPages: Math.ceil(total / pageSize),
+  }
+}
+
+export async function getAdminUserRoles(): Promise<string[]> {
+  const rows = await db.select({ name: roles.name }).from(roles)
+  return rows.map((r) => r.name)
+}