PHPLD Next 0.1.9

This release starts the language-pack foundation for multilingual PHPLD Next installs.

Changed

• Added English translation keys as the source of truth for new user-facing interface text.
• Added a starter Thai language pack for installer, login, public shell, admin navigation, and major settings labels.
• Added locale switching during installation and a default interface language setting in the admin area.
• Added request middleware that applies the selected locale across public, installer, and admin pages.
• Documented the language-pack maintenance approach: English keys are updated during normal development, while non-English packs can be refreshed in batches.