refactor: modernise RPM builder with Python tooling v2

- Migrate from legacy shell-based build system to modern Python tooling
- Update all metadata.yaml files to new schema with per-distro builds
- Standardise build scripts with curl -L, envsubst, and error handling
- Convert nfpm.yaml templates to use environment variable substitution
- Update Dockerfile to accept all package metadata as build arguments
- Modernise Makefile to use new Python build tool commands
- Update CI workflow to use tools/build instead of make

rpms/vault/resources/nfpm.yaml

@@ -1,17 +1,17 @@
 # nfpm.yaml
 
-name: vault
+name: ${PACKAGE_NAME}
 version: ${PACKAGE_VERSION}
 release: ${PACKAGE_RELEASE}
-arch: amd64
-platform: linux
+arch: ${PACKAGE_ARCH}
+platform: ${PACKAGE_PLATFORM}
 section: default
 priority: extra
-description: "Vault is a tool for securely accessing secrets. A secret is anything that you want to tightly control access to, such as API keys, passwords, certificates, and more. Vault provides a unified interface to any secret, while providing tight access control and recording a detailed audit log."
+description: "${PACKAGE_DESCRIPTION}"
 
-maintainer: HashiCorp
-homepage: https://github.com/hashicorp/vault
-license: BUSL-1.1
+maintainer: ${PACKAGE_MAINTAINER}
+homepage: ${PACKAGE_HOMEPAGE}
+license: ${PACKAGE_LICENSE}
 
 disable_globbing: false