feat(integrations,classisland,server,web,desktop): ClassIsland 联动插件——上报课表与上课状态、下发提醒并回执、教室端推送通道

教室机器上的 ClassIsland 现在可以直接和班级小助手互通：插件走 /api/integrations/classisland/*，用设备令牌（X-ClassIsland-Token，库里只存 sha256）独立鉴权，不占用 JWT 通道。

- 服务端：新增 integrations 模块（上报 / 待弹出 / 回执 / 课表镜像 / 回写），两个迁移（设备令牌表、Class.notificationChannel）；通知、叫人、联动页下发统一复用 pushToClassIsland，避免"某个页面发的通知不联动"
- 插件：packages/classisland-plugin（.NET 8，独立于 pnpm workspace）——BridgeService 上报与提醒轮询、ScheduleMapper/ClassPlanWriter 课表镜像、Avalonia 设置页、ClassHelperNotificationProvider 在 ClassIsland 上弹出提醒；本地/内网地址强制直连，躲开系统代理返回的假 404
- 客户端：设置页可选提醒通道（both / client / classisland），并订阅相应实时事件
- Web 端：新增「ClassIsland 联动」页（设备管理与提醒下发）
- 校验与打包：verify:classisland（需后端）、verify:classisland-plugin（静态契约 54 项）、build/dist:classisland-plugin 产出 .cipx
- 文档：README 与 AGENTS.md 同步新增联动说明，docs/screenshots/classisland 留三张真机截图

门禁：pnpm lint 0 error、pnpm typecheck 四包通过、verify:classisland-plugin 54/54 通过。运行期仍需在装了 ClassIsland 的机器上实测（步骤见 AGENTS.md §8）。

packages/server/prisma/migrations/20260927120000_add_classisland_integration/migration.sql

@@ -0,0 +1,58 @@
+-- ClassIsland 联动：设备接入 + 提醒下发
+--
+-- 说明：
+-- 1) IntegrationDevice 保存「班级 ↔ 一台装有联动插件的机器」的绑定关系，
+--    令牌只存 sha256 哈希，明文仅在创建/重置接口返回一次。
+-- 2) 同一班级内 deviceKey 唯一：插件重装后带同一机器码会重绑原记录，避免设备列表堆重复项。
+-- 3) ClassIslandPush 落库是为了「设备离线时通知不丢」：插件重连后拉取未确认的一条立即弹出。
+-- 4) 本文件重复执行是安全的（逐条执行、忽略"已存在"错误）。
+
+CREATE TABLE "IntegrationDevice" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "classId" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "deviceKey" TEXT NOT NULL,
+    "mode" TEXT NOT NULL DEFAULT 'plugin',
+    "enabled" BOOLEAN NOT NULL DEFAULT true,
+    "tokenHash" TEXT NOT NULL,
+    "tokenHint" TEXT NOT NULL,
+    "syncScheduleToServer" BOOLEAN NOT NULL DEFAULT true,
+    "mirrorScheduleToClassIsland" BOOLEAN NOT NULL DEFAULT false,
+    "classIslandVersion" TEXT,
+    "pluginVersion" TEXT,
+    "lastSeenAt" DATETIME,
+    "classPlanLoaded" BOOLEAN NOT NULL DEFAULT false,
+    "currentSubject" TEXT,
+    "currentTimeState" TEXT,
+    "currentPeriodStart" TEXT,
+    "currentPeriodEnd" TEXT,
+    "nextSubject" TEXT,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL,
+    CONSTRAINT "IntegrationDevice_classId_fkey" FOREIGN KEY ("classId") REFERENCES "Class" ("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+
+CREATE UNIQUE INDEX "IntegrationDevice_classId_deviceKey_key" ON "IntegrationDevice"("classId", "deviceKey");
+CREATE INDEX "IntegrationDevice_classId_idx" ON "IntegrationDevice"("classId");
+CREATE INDEX "IntegrationDevice_tokenHash_idx" ON "IntegrationDevice"("tokenHash");
+
+CREATE TABLE "ClassIslandPush" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "classId" TEXT NOT NULL,
+    "deviceId" TEXT,
+    "title" TEXT NOT NULL,
+    "content" TEXT NOT NULL,
+    "durationSeconds" INTEGER NOT NULL DEFAULT 8,
+    "speechContent" TEXT,
+    "urgent" BOOLEAN NOT NULL DEFAULT false,
+    "createdBy" TEXT,
+    "notificationId" TEXT,
+    "ackedAt" DATETIME,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "expiresAt" DATETIME NOT NULL,
+    CONSTRAINT "ClassIslandPush_classId_fkey" FOREIGN KEY ("classId") REFERENCES "Class" ("id") ON DELETE CASCADE ON UPDATE CASCADE,
+    CONSTRAINT "ClassIslandPush_deviceId_fkey" FOREIGN KEY ("deviceId") REFERENCES "IntegrationDevice" ("id") ON DELETE SET NULL ON UPDATE CASCADE
+);
+
+CREATE INDEX "ClassIslandPush_classId_createdAt_idx" ON "ClassIslandPush"("classId", "createdAt");
+CREATE INDEX "ClassIslandPush_deviceId_ackedAt_idx" ON "ClassIslandPush"("deviceId", "ackedAt");