Summary

• Adds Modern Standard Arabic (ar) localization at src/Caffeine/Resources/ar.lproj/Localizable.strings, covering all 30 user-facing strings from en.lproj.
• Registers ar in the project's knownRegions so the localization ships in the build.
• Adds an Added: Arabic translation. entry under [Unreleased] in CHANGELOG.md.

Notes

• Uses Modern Standard Arabic (formal register) for consistency with the other localizations.
• Arabic-Indic digits used for numeric durations (e.g. ٥ دقائق); the app name "Caffeine" is left in Latin script as a proper noun.

Test plan

• Build and run with the system language set to Arabic.
• Verify menu items, preferences window, and welcome message render correctly.
• Verify RTL layout behaves as expected in the preferences window.