feat(server): realtime handle & migration (#15487)

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

* **New Features**
  * Retry failed Copilot transcription tasks in real time.
  * Retried tasks resume processing and report updated status.
* Managed Copilot provider models can be omitted to use provider
defaults.

* **Bug Fixes**
* Improved handling of incomplete BYOK profiles, including safe
replacement of legacy records.
  * Duplicate profile creation now returns a clear validation error.
* Improved transcript processing reliability by preventing duplicate or
stale dispatches.

* **Migration**
* Consolidated legacy managed-provider settings while preserving
existing profiles and defaults.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/common/realtime/src/index.ts

@@ -83,6 +83,13 @@ export interface RealtimeRequestMap {
     };
     output: { task: unknown | null };
   };
+  'copilot.transcript.task.retry': {
+    input: {
+      workspaceId: string;
+      taskId: string;
+    };
+    output: { task: unknown | null };
+  };
   'user.quota-state.get': {
     input: Record<string, never>;
     output: { state: UserQuotaStateSnapshot };