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

#### PR Dependency Tree


* **PR #14934** 👈

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

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## 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)
<!-- end of auto-generated comment: release notes by coderabbit.ai -->


#### PR Dependency Tree


* **PR #14934** 👈
  * **PR #14936**

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

packages/backend/server/src/plugins/copilot/transcript/realtime.ts

@@ -0,0 +1,69 @@
+import { Injectable, OnModuleInit, Optional } from '@nestjs/common';
+import { z } from 'zod';
+
+import { CopilotTranscriptionJobNotFound } from '../../../base';
+import { AccessController } from '../../../core/permission';
+import type { RealtimeRegistry } from '../../../core/realtime';
+import { CopilotTranscriptionService, transcriptTaskRoom } from './service';
+
+@Injectable()
+export class CopilotTranscriptRealtimeProvider implements OnModuleInit {
+  constructor(
+    private readonly ac: AccessController,
+    private readonly transcript: CopilotTranscriptionService,
+    @Optional() private readonly registry?: RealtimeRegistry
+  ) {}
+
+  onModuleInit() {
+    this.registry?.registerRequest({
+      name: 'copilot.transcript.task.get',
+      input: z
+        .object({
+          workspaceId: z.string(),
+          blobId: z.string().optional(),
+          taskId: z.string().optional(),
+        })
+        .refine(input => input.blobId || input.taskId),
+      handle: async (user, input) => {
+        await this.assertCopilot(user.id, input.workspaceId);
+        return {
+          task: await this.transcript.queryTask(
+            user.id,
+            input.workspaceId,
+            input.taskId,
+            input.blobId
+          ),
+        };
+      },
+    });
+
+    this.registry?.registerTopic({
+      name: 'copilot.transcript.task.changed',
+      input: z.object({
+        workspaceId: z.string(),
+        taskId: z.string(),
+      }),
+      authorize: async (user, input) => {
+        await this.assertCopilot(user.id, input.workspaceId);
+        const task = await this.transcript.queryTask(
+          user.id,
+          input.workspaceId,
+          input.taskId
+        );
+        if (!task) {
+          throw new CopilotTranscriptionJobNotFound();
+        }
+      },
+      room: (_user, input) =>
+        transcriptTaskRoom(input.workspaceId, input.taskId),
+    });
+  }
+
+  private async assertCopilot(userId: string, workspaceId: string) {
+    await this.ac
+      .user(userId)
+      .workspace(workspaceId)
+      .allowLocal()
+      .assert('Workspace.Copilot');
+  }
+}