feat(server): realtime notification & task status (#14934)

#### PR Dependency Tree


* **PR #14934** 👈

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **New Features**
* Full realtime platform added: live notifications, comments, embedding
progress, and transcription task updates via realtime subscriptions.

* **Chores**
* Frontend switched from polling/GraphQL queries to realtime channels;
legacy query fields marked deprecated and client libs updated to use
realtime APIs.

[![Review Change
Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/toeverything/AFFiNE/pull/14934)
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#### PR Dependency Tree


* **PR #14934** 👈
  * **PR #14936**

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

packages/backend/server/src/app.module.ts

@@ -42,6 +42,7 @@ import { NotificationModule } from './core/notification';
 import { PermissionModule } from './core/permission';
 import { QueueDashboardModule } from './core/queue-dashboard';
 import { QuotaModule } from './core/quota';
+import { RealtimeModule } from './core/realtime';
 import { SelfhostModule } from './core/selfhost';
 import { StaticFileModule } from './core/static-files';
 import { StorageModule } from './core/storage';
@@ -117,6 +118,7 @@ export const FunctionalityModules = [
   ErrorModule,
   WebSocketModule,
   JobModule.forRoot(),
+  RealtimeModule,
   ModelsModule,
   ScheduleModule.forRoot(),
   MonitorModule,