refactor: move Maven POM and publication logic into gradle/maven-pom.gradle
feat: publish signed mavenJava artifacts with sources and Javadoc jars
feat: add Central staging, checksum generation, and centralBundle packaging
feat: add packageReleaseCandidate task for clean local release verification
docs: define Maven POM metadata for org.egothor:radixor
docs: switch project licensing metadata and repository license file to BSD-3-Clause
ci: build signed Central bundle in tagged release workflow
ci: upload Central bundle to Maven Central via Sonatype Portal API
ci: attach Central bundle to GitHub release assets
