fix(ui): checkout button label when adding seats to a free trial

[mauricioabreu]

Fix checkout button label showing "Start free trial" when adding seats during a free trial period

Description

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

Summary by CodeRabbit

Bug Fixes

• Fixed checkout button label incorrectly displaying "Start free trial" when adding seats during an active free trial period; now correctly shows the appropriate payment label.