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

Dockerfile

@@ -7,10 +7,25 @@ RUN mkdir -p /app/dist
 # Set working directory
 WORKDIR /app
 
-ARG PACKAGE_RELEASE
-ENV PACKAGE_RELEASE=${PACKAGE_RELEASE}
+# Accept all package metadata as build arguments and set as environment variables
+ARG PACKAGE_NAME
+ENV PACKAGE_NAME=${PACKAGE_NAME}
 ARG PACKAGE_VERSION
 ENV PACKAGE_VERSION=${PACKAGE_VERSION}
+ARG PACKAGE_RELEASE
+ENV PACKAGE_RELEASE=${PACKAGE_RELEASE}
+ARG PACKAGE_DESCRIPTION
+ENV PACKAGE_DESCRIPTION=${PACKAGE_DESCRIPTION}
+ARG PACKAGE_MAINTAINER
+ENV PACKAGE_MAINTAINER=${PACKAGE_MAINTAINER}
+ARG PACKAGE_HOMEPAGE
+ENV PACKAGE_HOMEPAGE=${PACKAGE_HOMEPAGE}
+ARG PACKAGE_LICENSE
+ENV PACKAGE_LICENSE=${PACKAGE_LICENSE}
+ARG PACKAGE_ARCH
+ENV PACKAGE_ARCH=${PACKAGE_ARCH}
+ARG PACKAGE_PLATFORM
+ENV PACKAGE_PLATFORM=${PACKAGE_PLATFORM}
 
 # Copy resources from the context into the container
 COPY resources /app/resources