Removed static method-level fallback. Shipping method selector now:
1. Shows 'Enter shipping address to see available rates' when address incomplete
2. Calls calculate_shipping endpoint to get actual WC_Shipping_Rate objects
3. Displays rate-level options (e.g., JNE REG, JNE YES) not method-level
This ensures third-party shipping plugins like Rajaongkir, UPS, FedEx
display their courier rates correctly.