refactor: modernise RPM builder with Python tooling

- Replace Makefile version/release file system with metadata.yaml only
- Add Python build automation (./tools/build) with Gitea API integration
- Add GitHub release updater (./tools/update-gh) for version management
- Centralize Dockerfiles into single parameterized Dockerfile
- Remove 54+ individual package Dockerfiles and version directories
- Update Makefile to use new Python tooling
- Add GITEA_API_TOKEN validation to prevent duplicate builds
- Support both explicit version/release args and metadata.yaml reading

Dockerfile

@@ -0,0 +1,19 @@
+ARG BASE_IMAGE=git.unkin.net/unkin/almalinux9-rpmbuilder:latest
+FROM ${BASE_IMAGE}
+
+# Create output directory for RPMs
+RUN mkdir -p /app/dist
+
+# Set working directory
+WORKDIR /app
+
+ARG PACKAGE_RELEASE
+ENV PACKAGE_RELEASE=${PACKAGE_RELEASE}
+ARG PACKAGE_VERSION
+ENV PACKAGE_VERSION=${PACKAGE_VERSION}
+
+# Copy resources from the context into the container
+COPY resources /app/resources
+
+# Default command to build RPMs
+CMD /app/resources/build.sh