fix(server): realtime loading (#14959)

#### PR Dependency Tree


* **PR #14959** 👈

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

* **Refactor**
* Rewired realtime and copilot services to require their runtime
dependencies, improving reliability and removing nullable/optional
runtime paths.

* **Tests**
* Centralized service creation in tests with helper factories and added
checks ensuring realtime dependency injection is configured as expected.

<!-- review_stack_entry_start -->

[![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/14959)

<!-- review_stack_entry_end -->
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -1,10 +1,10 @@
-import { Injectable, OnModuleInit, Optional } from '@nestjs/common';
+import { Injectable, OnModuleInit } from '@nestjs/common';
 import { z } from 'zod';
 
 import { CopilotTranscriptionJobNotFound } from '../../../base';
 import { AccessController } from '../../../core/permission';
 import {
-  type RealtimeRegistry,
+  RealtimeRegistry,
   realtimeTranscriptTaskRoom,
   registerRealtimeLiveQuery,
 } from '../../../core/realtime';
@@ -15,7 +15,7 @@ export class CopilotTranscriptRealtimeProvider implements OnModuleInit {
   constructor(
     private readonly ac: AccessController,
     private readonly transcript: CopilotTranscriptionReader,
-    @Optional() private readonly registry?: RealtimeRegistry
+    private readonly registry: RealtimeRegistry
   ) {}
 
   onModuleInit() {