Add macOS .dmg installer to release workflow

[PrenSJ2]

Summary

• Add native macOS .dmg installer build to the release workflow
• macOS builds run in parallel with Windows builds
• DMG includes bundled JRE with JavaFX, so users don't need Java installed

Changes

• Add installer/init-macos script to prepare macOS build resources (icon, licenses, JavaFX jmods)
• Add publish-macos job to release workflow using jlink + jpackage

Technical Details

• Uses jlink to create a custom runtime with JavaFX native libraries properly included
• Downloads JavaFX 21.0.5 jmods from Gluon at build time
• Converts PNG icon to .icns format using macOS native tools
• Detects architecture (aarch64/x64) automatically

Output

• MCA_Selector_Setup.dmg (~180MB) - native macOS app bundle with bundled JRE