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/test_kubernetes.py

@@ -326,7 +326,7 @@ nodes:
     project_root = BASE_DIR.parent
     subprocess.run(
         ["docker", "build", "-t", "byjg/easy-haproxy:local",
-         "-f", str(project_root / "build" / "Dockerfile"),
+         "-f", str(project_root / "deploy" / "docker" / "Dockerfile"),
          str(project_root)],
         check=True,
         capture_output=True,