Normalize zipnote filename diff ordering

[AgentGoose32]

Fixes #442

Summary

• Normalizes diffoscope zipnote filename diffs before storing job results.
• Sorts removed and added Filename: entries by their path after the package/version prefix, so equivalent files line up instead of being paired by archive root/version order.
• Applies the normalization recursively to nested diffoscope details and leaves non-zipnote diffs untouched.
• Adds regression coverage for the misordered zipnote filename case.

Validation

• bundle install with Homebrew Ruby 4.0.3
• bundle exec ruby -c app/models/job.rb
• bundle exec ruby -c test/models/job_test.rb
• zipnote sort smoke test
• git diff --check

Note: full bundle exec rails test test/models/job_test.rb is blocked locally because the repo expects PostgreSQL on /tmp/.s.PGSQL.5432.