v3.18.0

Modular billing parity\n\n- Added after-commit mutation events across billing core, catalog, pricing, orders, invoicing, payments, and hosting.\n- Added checkout and quote-to-order lifecycle events.\n- Completed modular provider foundations for cPanel, DirectAdmin, Virtualmin, Plesk, Liberu Control Panel, Enom, and ResellerClub.\n- Synchronized the development branch with main.\n\n## Verification\n\n- 993 tests passed, 3 skipped\n- 2,775 assertions\n- PHPStan, Pint, module validation, Composer validation, and diff checks passed.