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/nzbget/resources/build.sh

@@ -1,5 +1,7 @@
 #!/usr/bin/bash
 
+set -e
+
 # Download the pre-built RPM from GitHub releases
-curl -o /app/dist/nzbget-${PACKAGE_VERSION}-${PACKAGE_RELEASE}.x86_64.rpm \
+curl -L -o /app/dist/nzbget-${PACKAGE_VERSION}-${PACKAGE_RELEASE}.x86_64.rpm \
   https://github.com/nzbgetcom/nzbget/releases/download/v$PACKAGE_VERSION/nzbget-${PACKAGE_VERSION}-${PACKAGE_RELEASE}.x86_64.rpm

rpms/nzbget/resources/nfpm.yaml

@@ -1,17 +1,17 @@
 # nfpm.yaml
 
-name: nzbget
+name: ${PACKAGE_NAME}
 version: ${PACKAGE_VERSION}
 release: ${PACKAGE_RELEASE}
-arch: amd64
-platform: linux
+arch: ${PACKAGE_ARCH}
+platform: ${PACKAGE_PLATFORM}
 section: default
 priority: extra
-description: "NZBGet is a binary downloader, which downloads files from Usenet based-on information given in nzb files."
+description: "${PACKAGE_DESCRIPTION}"
 
-maintainer: nzbgetcom
-homepage: https://github.com/nzbgetcom/nzbget
-license: GPL-2.0
+maintainer: ${PACKAGE_MAINTAINER}
+homepage: ${PACKAGE_HOMEPAGE}
+license: ${PACKAGE_LICENSE}
 
 disable_globbing: false