phsl / new-api

Enhance the UI of payment method selection area with responsive layouts:
- Use 2-column grid when exactly 2 payment methods are present
- Use 3-column grid for 3 payment methods
- Use compact card layout for more than 3 payment methods
- Full-width button for single payment method

This improves the visual balance across different device sizes and payment provider configurations, ensuring buttons fill their grid cells appropriately with the w-full class.