refactor: P0-3/5/6 解耦修复 - 循环依赖/通知分发/课表写入口

P0-3: 修复 shared/lib <-> auth 循环依赖
- audit-logger.ts, change-logger.ts, auth-guard.ts, classes/data-access.ts
  改用动态 import("@/auth") 打破静态模块级循环依赖
- shared/lib 不再静态导入 @/auth

P0-5: messaging 改用 notifications dispatcher
- messaging/actions.ts 的 sendMessageAction 改用 sendNotification
  替代直接调用 createNotification
- 用户通知偏好(SMS/微信/邮件/站内)现在被正确尊重

P0-6: 统一 classSchedule 写入口到 scheduling/data-access
- 新增 insertClassScheduleItem/updateClassScheduleItemById/
  deleteClassScheduleItemById/replaceClassSchedule 统一写入函数
- classes/data-access.ts 的三个 schedule 写入函数委托给 scheduling
- scheduling/actions.ts 的 applyAutoScheduleAction 改用 replaceClassSchedule
- 移除 scheduling/actions.ts 中不再使用的 classSchedule/createId 导入

验证: tsc --noEmit 0 errors, npm run lint 0 errors

src/modules/classes/data-access.ts

@@ -5,7 +5,6 @@ import { cache } from "react"
 import { and, asc, desc, eq, inArray, isNull, or, sql, type SQL } from "drizzle-orm"
 import { createId } from "@paralleldrive/cuid2"
 
-import { auth } from "@/auth"
 import { db } from "@/shared/db"
 import {
   classes,
@@ -24,6 +23,11 @@ import {
   users,
   usersToRoles,
 } from "@/shared/db/schema"
+import {
+  insertClassScheduleItem,
+  updateClassScheduleItemById,
+  deleteClassScheduleItemById,
+} from "@/modules/scheduling/data-access"
 import { DEFAULT_CLASS_SUBJECTS } from "./types"
 import type {
   AdminClassListItem,
@@ -47,6 +51,7 @@ import type {
 } from "./types"
 
 const getSessionTeacherId = async (): Promise<string | null> => {
+  const { auth } = await import("@/auth")
   const session = await auth()
   const userId = String(session?.user?.id ?? "").trim()
   if (!userId) return null
@@ -1859,9 +1864,8 @@ export async function createClassScheduleItem(data: CreateClassScheduleItemInput
 
   if (!owned) throw new Error("Class not found")
 
-  const id = createId()
-  await db.insert(classSchedule).values({
-    id,
+  // Delegate DB write to scheduling module (unified write entry point)
+  return insertClassScheduleItem({
     classId,
     weekday,
     startTime,
@@ -1869,8 +1873,6 @@ export async function createClassScheduleItem(data: CreateClassScheduleItemInput
     course,
     location,
   })
-
-  return id
 }
 
 export async function updateClassScheduleItem(scheduleId: string, data: UpdateClassScheduleItemInput): Promise<void> {
@@ -1944,10 +1946,8 @@ export async function updateClassScheduleItem(scheduleId: string, data: UpdateCl
 
   if (Object.keys(update).length === 0) return
 
-  await db
-    .update(classSchedule)
-    .set(update)
-    .where(eq(classSchedule.id, id))
+  // Delegate DB write to scheduling module (unified write entry point)
+  await updateClassScheduleItemById(id, update)
 }
 
 export async function deleteClassScheduleItem(scheduleId: string): Promise<void> {
@@ -1964,7 +1964,8 @@ export async function deleteClassScheduleItem(scheduleId: string): Promise<void>
 
   if (!owned) throw new Error("Schedule item not found")
 
-  await db.delete(classSchedule).where(eq(classSchedule.id, id))
+  // Delegate DB write to scheduling module (unified write entry point)
+  await deleteClassScheduleItemById(id)
 }
 
 export const getStudentsSubjectScores = cache(