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/.dockerignore

@@ -0,0 +1,11 @@
+node_modules
+dist
+.git
+.gitignore
+.angular
+.vscode
+*.md
+.editorconfig
+.prettierrc
+src/test.ts
+**/*.spec.ts