build: move source/javadoc plugins to release profile

[marevol]

Summary

Move release-only plugins (source and javadoc jar generation) into the release profile so they run only during release:perform, completing the release configuration cleanup started by moving GPG signing into the profile.

Changes Made

• Moved maven-source-plugin (attach-sources) and maven-javadoc-plugin (attach-javadocs) from the main build into the release profile, alongside maven-gpg-plugin
• maven-release-plugin already activates the profile via <releaseProfiles>release</releaseProfiles>, per the maven-release-plugin 2→3 migration guide (https://maven.apache.org/maven-release/maven-release-plugin/migrate.html)

Testing

• mvn package -DskipTests — no sources/javadoc jars produced, no GPG required for local builds
• mvn package -P release -DskipTests -Dgpg.skip=true — sources and javadoc jars are produced

Additional Notes

• Plain mvn install no longer attaches sources/javadoc jars locally; they are generated only during releases.
• The same standardization is applied across other CodeLibs repositories (corelib, curl4j, jcifs, jhighlight, nekohtml, spnego, java-saml, fess-parent).