feat(proxy): add service CRUD with persistent storage

ServiceManager with JSON file persistence replaces static env var config.
CRUD API endpoints (POST/PUT/DELETE /api/services) with WebSocket broadcast.
Dashboard: add/edit/delete services via modal form.

Co-Authored-By: Claude <noreply@anthropic.com>

packages/shared/src/types/proxy.ts

@@ -32,6 +32,7 @@ export type WsMessageType =
   | 'state_change'
   | 'status_update'
   | 'service_health'
+  | 'service_list_changed'
   | 'log';
 
 export interface WsMessage {