feat(announcements,messaging,notifications): 实现所有长期问题 — SSE 实时推送 + 通知日志持久化 + 优先级/归档 + 消息星标/草稿 + 公告已读回执/置顶 + 分类筛选/桌面推送 + 测试覆盖

P1-8 通知实时推送（SSE）:
- 新增 /api/notifications/stream SSE 端点（15 秒推送，5 分钟超时）
- 新增 useNotificationStream Hook（SSE + 轮询降级）
- NotificationDropdown 改用 SSE 实时推送

P2-12 测试覆盖:
- notifications/dispatcher.test.ts（6 个测试，渠道选择逻辑）
- notifications/channels/in-app-channel.test.ts（9 个测试，类型映射）
- messaging/schema.test.ts（34 个测试，Zod 校验）
- tests/e2e/messages.spec.ts（消息模块 E2E 测试）
- vitest.unit.config.ts 添加 server-only stub

P2-13a 通知发送日志持久化:
- 新增 notification_logs 表（userId/title/channel/status/messageId/error/sentAt）
- logNotificationSend 改为 async 写入 DB（失败降级 console）
- dispatcher 传递 payload 用于持久化

P2-13b 通知优先级和归档:
- messageNotifications 表新增 priority（low/normal/high/urgent）和 isArchived 字段
- getNotifications 支持归档和优先级筛选
- 新增 archiveNotificationAction
- NotificationList 显示优先级 Badge 和归档按钮

P2-13c 消息星标和草稿:
- messages 表新增 isStarred 字段
- 新增 message_drafts 表
- 新增 toggleMessageStar + 草稿 CRUD Server Actions
- 新增 5 个草稿 data-access 函数

P2-13d 公告已读回执和置顶:
- announcements 表新增 isPinned 字段
- 新增 announcement_reads 表（唯一索引保证幂等）
- 新增 toggleAnnouncementPinAction + markAnnouncementAsReadAction
- getAnnouncements 排序置顶优先

P2-13e 通知分类筛选和桌面推送:
- NotificationList 添加按类型筛选按钮组
- 新增 useDesktopNotifications Hook（浏览器 Notification API）
- NotificationDropdown 集成桌面推送（新通知触发）

架构图同步:
- 004 和 005 均已更新（新增表、Action、Hook、组件描述）

src/modules/announcements/data-access.ts

@@ -1,10 +1,11 @@
 import "server-only"
 
 import { cache } from "react"
-import { and, desc, eq, or } from "drizzle-orm"
+import { createId } from "@paralleldrive/cuid2"
+import { and, count, desc, eq, inArray, or } from "drizzle-orm"
 
 import { db } from "@/shared/db"
-import { announcements, users } from "@/shared/db/schema"
+import { announcements, announcementReads, users } from "@/shared/db/schema"
 import type {
   Announcement,
   AnnouncementInsertData,
@@ -30,6 +31,7 @@ const mapRow = (
     authorId: string
     authorName: string | null
     publishedAt: Date | null
+    isPinned: boolean
     createdAt: Date
     updatedAt: Date
   }
@@ -44,6 +46,7 @@ const mapRow = (
   authorId: row.authorId,
   authorName: row.authorName,
   publishedAt: toIso(row.publishedAt),
+  isPinned: row.isPinned,
   createdAt: toIsoRequired(row.createdAt),
   updatedAt: toIsoRequired(row.updatedAt),
 })
@@ -93,13 +96,14 @@ export const getAnnouncements = cache(
         authorId: announcements.authorId,
         authorName: users.name,
         publishedAt: announcements.publishedAt,
+        isPinned: announcements.isPinned,
         createdAt: announcements.createdAt,
         updatedAt: announcements.updatedAt,
       })
       .from(announcements)
       .leftJoin(users, eq(users.id, announcements.authorId))
       .where(conditions.length > 0 ? and(...conditions) : undefined)
-      .orderBy(desc(announcements.createdAt))
+      .orderBy(desc(announcements.isPinned), desc(announcements.createdAt))
       .limit(pageSize)
       .offset(offset)
 
@@ -121,6 +125,7 @@ export const getAnnouncementById = cache(
         authorId: announcements.authorId,
         authorName: users.name,
         publishedAt: announcements.publishedAt,
+        isPinned: announcements.isPinned,
         createdAt: announcements.createdAt,
         updatedAt: announcements.updatedAt,
       })
@@ -197,6 +202,94 @@ export async function archiveAnnouncementById(id: string): Promise<void> {
     .where(eq(announcements.id, id))
 }
 
+// ---------------------------------------------------------------------------
+// V2-P2-13d: 公告置顶
+// ---------------------------------------------------------------------------
+
+export async function toggleAnnouncementPin(id: string): Promise<void> {
+  // 查询当前置顶状态
+  const [row] = await db
+    .select({ isPinned: announcements.isPinned })
+    .from(announcements)
+    .where(eq(announcements.id, id))
+    .limit(1)
+
+  if (!row) return
+
+  await db
+    .update(announcements)
+    .set({ isPinned: !row.isPinned, updatedAt: new Date() })
+    .where(eq(announcements.id, id))
+}
+
+// ---------------------------------------------------------------------------
+// V2-P2-13d: 公告已读回执（announcement_reads 表）
+// ---------------------------------------------------------------------------
+
+/**
+ * 标记公告为已读（如果尚未标记）。
+ * 使用 INSERT IGNORE 语义避免重复插入（依赖唯一索引）。
+ */
+export async function markAnnouncementAsRead(announcementId: string, userId: string): Promise<void> {
+  // 先检查是否已存在已读记录
+  const [existing] = await db
+    .select({ id: announcementReads.id })
+    .from(announcementReads)
+    .where(and(eq(announcementReads.announcementId, announcementId), eq(announcementReads.userId, userId)))
+    .limit(1)
+
+  if (existing) return
+
+  const id = createId()
+  await db.insert(announcementReads).values({
+    id,
+    announcementId,
+    userId,
+  })
+}
+
+/**
+ * 检查用户是否已读指定公告。
+ */
+export async function isAnnouncementReadByUser(announcementId: string, userId: string): Promise<boolean> {
+  const [row] = await db
+    .select({ id: announcementReads.id })
+    .from(announcementReads)
+    .where(and(eq(announcementReads.announcementId, announcementId), eq(announcementReads.userId, userId)))
+    .limit(1)
+  return !!row
+}
+
+/**
+ * 获取公告的已读用户数。
+ */
+export async function getAnnouncementReadCount(announcementId: string): Promise<number> {
+  const [row] = await db
+    .select({ value: count() })
+    .from(announcementReads)
+    .where(eq(announcementReads.announcementId, announcementId))
+  return Number(row?.value ?? 0)
+}
+
+/**
+ * 批量获取用户对多个公告的已读状态。
+ * 返回 Map<announcementId, boolean>
+ */
+export async function getAnnouncementReadStatusForUser(
+  announcementIds: string[],
+  userId: string
+): Promise<Map<string, boolean>> {
+  if (announcementIds.length === 0) return new Map()
+
+  const rows = await db
+    .select({ announcementId: announcementReads.announcementId })
+    .from(announcementReads)
+    .where(and(eq(announcementReads.userId, userId), inArray(announcementReads.announcementId, announcementIds)))
+
+  const readSet = new Set(rows.map((r) => r.announcementId))
+  return new Map(announcementIds.map((id) => [id, readSet.has(id)]))
+}
+
 /**
  * 管理端公告列表页编排函数：一次性获取公告列表、年级列表、班级列表。
  * 将原本散落在 page.tsx 中的多模块编排逻辑下沉到 data-access 层，