feat: landing via nginx:alpine container with volume mount

- Removed Dockerfile build; uses nginx:alpine image + read-only volume mount
- landing/src/ mounted as /usr/share/nginx/html:ro
- nginx.conf mounted as /etc/nginx/conf.d/default.conf:ro
- Healthcheck on /health.json

docker/docker-compose.landing.yml

@@ -1,13 +1,12 @@
-version: '3.8'
-
 services:
   landing:
-    build:
-      context: ../landing
-      dockerfile: Dockerfile
+    image: nginx:alpine
     container_name: phantom-landing
     ports:
       - "8080:80"
+    volumes:
+      - ../landing/src:/usr/share/nginx/html:ro
+      - ../landing/nginx.conf:/etc/nginx/conf.d/default.conf:ro
     environment:
       - API_STATUS_URL=${API_STATUS_URL:-http://host.docker.internal:3000/api/status}
     restart: unless-stopped