CUB-66: scaffold Angular frontend and add Dockerfile with nginx

- Scaffolded Angular 21 app in frontend/ (standalone, routing, scss)
- Multi-stage Dockerfile: node:22-alpine build → nginx:alpine serve
- nginx.conf with SPA routing fallback, API proxy, gzip, asset caching
- .dockerignore excludes node_modules, dist, .angular, spec files
- docker build → PASS, container serves UI on port 80 (HTTP 200)
- Final image: 92.9MB (nginx:alpine)

frontend/package.json

@@ -0,0 +1,32 @@
+{
+  "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,
+  "packageManager": "npm@11.11.0",
+  "dependencies": {
+    "@angular/common": "^21.2.0",
+    "@angular/compiler": "^21.2.0",
+    "@angular/core": "^21.2.0",
+    "@angular/forms": "^21.2.0",
+    "@angular/platform-browser": "^21.2.0",
+    "@angular/router": "^21.2.0",
+    "rxjs": "~7.8.0",
+    "tslib": "^2.3.0"
+  },
+  "devDependencies": {
+    "@angular/build": "^21.2.8",
+    "@angular/cli": "^21.2.8",
+    "@angular/compiler-cli": "^21.2.0",
+    "jsdom": "^28.0.0",
+    "prettier": "^3.8.1",
+    "typescript": "~5.9.2",
+    "vitest": "^4.0.8"
+  }
+}