feat(server): converge legacy compatibility (#15426)

#### PR Dependency Tree


* **PR #15426** 👈

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**
* Added workspace BYOK profiles with provider/model catalogs, capability
validation, connection probing, credential rotation, reordering, and
secure local leases.
* Added Copilot route options, selectable targets, managed tiers,
explicit profile/model overrides, and improved streaming with tool
callbacks and abort support.
* Added Copilot availability controls to prevent access when the feature
is disabled.
* **Changes**
* Simplified Copilot configuration and removed legacy provider-specific
settings.
* Removed obsolete model, token-cost, transcript strategy, and provider
metadata fields from public responses.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -1,13 +1,15 @@
 import { Injectable, OnModuleInit } from '@nestjs/common';
 import { z } from 'zod';
 
-import { CopilotTranscriptionJobNotFound } from '../../../base';
+import { Config } from '../../../base/config';
+import { CopilotTranscriptionJobNotFound } from '../../../base/error/errors.gen';
 import { PermissionAccess } from '../../../core/permission';
 import {
   RealtimeRegistry,
   realtimeTranscriptTaskRoom,
   registerRealtimeLiveQuery,
 } from '../../../core/realtime';
+import { assertCopilotEnabled } from '../availability';
 import { CopilotTranscriptionReader } from './reader';
 
 @Injectable()
@@ -15,7 +17,8 @@ export class CopilotTranscriptRealtimeProvider implements OnModuleInit {
   constructor(
     private readonly ac: PermissionAccess,
     private readonly transcript: CopilotTranscriptionReader,
-    private readonly registry: RealtimeRegistry
+    private readonly registry: RealtimeRegistry,
+    private readonly config: Config
   ) {}
 
   onModuleInit() {
@@ -68,6 +71,7 @@ export class CopilotTranscriptRealtimeProvider implements OnModuleInit {
   }
 
   private async assertCopilot(userId: string, workspaceId: string) {
+    assertCopilotEnabled(this.config);
     await this.ac
       .user(userId)
       .workspace(workspaceId)