Migrate build assets and scripts to deploy/docker structure

- Removed `install.sh` and moved Docker-related assets to `deploy/docker`.
- Updated all Dockerfile references from `build/` to `deploy/docker/`.
- Refactored paths in E2E tests, Makefile, and documentation for consistency with new directory structure.
- Added `HAPROXY_STATS_CORS_ORIGIN` environment variable in `docker-compose.yml`.

tests_e2e/static/docker-compose.yml

@@ -63,7 +63,7 @@ services:
     image: byjg/easy-haproxy:local
     build:
       context: ../..
-      dockerfile: build/Dockerfile
+      dockerfile: deploy/docker/Dockerfile
     volumes:
       - ./conf/:/etc/easyhaproxy/static/
       - ../static/host1.local.pem:/etc/easyhaproxy/certs/haproxy/host1.local.pem:ro