feat(CUB-58): Agent Status SignalR Service (Angular)

- Scaffold Angular 17 frontend with standalone components
- Add @microsoft/signalr package dependency
- Create AgentStatusService connecting to /hub endpoint
  - Auto-reconnect with progressive delays
  - Listens for AgentStatusChanged and BroadcastMessage
  - Logs all updates to console
  - Exposes statusUpdates$ and connected$ observables
  - onStatusUpdate() alias matching CUB-58 spec
- Create AgentStatusUpdate interface (agentId, status, lastSeenAt)
- Add APP_INITIALIZER provider to start connection on app boot
- Register initializer in app.config.ts
- Update .gitignore for frontend build artifacts

frontend/README.md

@@ -0,0 +1,27 @@
+# Frontend
+
+This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 17.3.17.
+
+## Development server
+
+Run `ng serve` for a dev server. Navigate to `http://localhost:4200/`. The application will automatically reload if you change any of the source files.
+
+## Code scaffolding
+
+Run `ng generate component component-name` to generate a new component. You can also use `ng generate directive|pipe|service|class|guard|interface|enum|module`.
+
+## Build
+
+Run `ng build` to build the project. The build artifacts will be stored in the `dist/` directory.
+
+## Running unit tests
+
+Run `ng test` to execute the unit tests via [Karma](https://karma-runner.github.io).
+
+## Running end-to-end tests
+
+Run `ng e2e` to execute the end-to-end tests via a platform of your choice. To use this command, you need to first add a package that implements end-to-end testing capabilities.
+
+## Further help
+
+To get more help on the Angular CLI use `ng help` or go check out the [Angular CLI Overview and Command Reference](https://angular.io/cli) page.