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/unrar/resources/build.sh

@@ -1,10 +1,14 @@
 #!/usr/bin/bash
 
+set -e
+
 # Download and extract unrar (with version formatting)
 export DOWNLOAD_VERSION=$(echo $PACKAGE_VERSION | sed s/\\.//)
-curl -o /app/rarlinux.tar.gz https://www.rarlab.com/rar/rarlinux-x64-${DOWNLOAD_VERSION}.tar.gz
+curl -L -o /app/rarlinux.tar.gz https://www.rarlab.com/rar/rarlinux-x64-${DOWNLOAD_VERSION}.tar.gz
 tar xf /app/rarlinux.tar.gz
 mv /app/rar/unrar /app/
 
-# Build the RPM
-nfpm pkg --config /app/resources/nfpm.yaml --target /app/dist --packager rpm
+# Process the nfpm.yaml template with environment variables
+envsubst < /app/resources/nfpm.yaml > /app/nfpm.yaml
+
+nfpm pkg --config /app/nfpm.yaml --target /app/dist --packager rpm