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/.prettierrc

@@ -0,0 +1,12 @@
+{
+  "printWidth": 100,
+  "singleQuote": true,
+  "overrides": [
+    {
+      "files": "*.html",
+      "options": {
+        "parser": "angular"
+      }
+    }
+  ]
+}