Add Docker, NGINX config, and CI workflow

Introduces Dockerfile and nginx.conf for containerized deployment of the Angular frontend. Adds a GitHub Actions workflow for automated Docker image build and push. Updates README with setup, tech stack, and deployment instructions.

.github/workflows/docker.yml

@@ -0,0 +1,19 @@
+name: Build & Push Frontend
+on:
+  push:
+    branches: [ main ]
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: docker.io/${{ secrets.DOCKERHUB_USERNAME }}/playground-frontend:main