fix: parse Maven license metadata from JARs

[AgentGoose32]

Summary

• parse Maven pom.xml license metadata when handling JAR uploads
• preserve the full JAR layout instead of stripping the first path component
• reuse the existing Licensee JSON shape for licenses discovered from package metadata

Validation

• PATH=/opt/homebrew/opt/ruby/bin:$PATH bundle exec rails db:create db:schema:load
• PATH=/opt/homebrew/opt/ruby/bin:$PATH bundle exec rails test test/models/job_test.rb (7 runs, 14 assertions, 0 failures)

Fixes #153