build(maven): modernize Java and reproducible build settings

[mivek]

Summary

• preserve the Java 17 compiler release adopted on main
• define UTF-8 reporting output and reproducible-build timestamps
• enforce Maven 3.9 or later and Java 17 or later for the build

Testing

• rebased onto current main and resolved the POM conflict
• Java 17 Maven validate and test reactor passed
• Java 21 Enforcer validation passed (Checkstyle skipped because sandbox DNS could not resolve checkstyle.org)
• earlier clean package builds verified reproducible JAR hashes and semantic-release versions:set behavior

[github-actions]

Please check on sonarcloud https://sonarcloud.io/project/pull_requests_list?id=io.github.mivek%3AmetarParser that the PR does not add any issue.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud