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/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "frontend",
+  "version": "0.0.0",
+  "scripts": {
+    "ng": "ng",
+    "start": "ng serve",
+    "build": "ng build",
+    "watch": "ng build --watch --configuration development",
+    "test": "ng test"
+  },
+  "private": true,
+  "dependencies": {
+    "@angular/animations": "^17.3.0",
+    "@angular/common": "^17.3.0",
+    "@angular/compiler": "^17.3.0",
+    "@angular/core": "^17.3.0",
+    "@angular/forms": "^17.3.0",
+    "@angular/material": "^17.3.10",
+    "@angular/platform-browser": "^17.3.0",
+    "@angular/platform-browser-dynamic": "^17.3.0",
+    "@angular/router": "^17.3.0",
+    "@microsoft/signalr": "^10.0.0",
+    "rxjs": "~7.8.0",
+    "tslib": "^2.3.0",
+    "zone.js": "~0.14.3"
+  },
+  "devDependencies": {
+    "@angular-devkit/build-angular": "^17.3.17",
+    "@angular/cli": "^17.3.17",
+    "@angular/compiler-cli": "^17.3.0",
+    "@types/jasmine": "~5.1.0",
+    "jasmine-core": "~5.1.0",
+    "karma": "~6.4.0",
+    "karma-chrome-launcher": "~3.2.0",
+    "karma-coverage": "~2.2.0",
+    "karma-jasmine": "~5.1.0",
+    "karma-jasmine-html-reporter": "~2.1.0",
+    "typescript": "~5.4.2"
+  }
+}