Add refund action to booking list/detail with full-refund toggle

- New RefundBookingTableAction on the booking list row and detail page,
  refunding a Confirmed booking directly via RefundBookingAction — no need
  to hunt up its Payment on the Refunds resource first.
- Payment::refundableBalance() extracted from RefundBookingAction's private
  balance check so both refund forms can display and cap against it.
- RefundBookingAction::resolveRefundablePayment() made public for the same
  reason (round-trip leg resolution reused by the UI).
- Both refund forms (ProcessRefundAction and the new booking action) gain a
  "Full refund" toggle, on by default, which refunds the payment's whole
  remaining balance without requiring a manually typed amount. Turning it
  off reveals an amount field capped at the refundable balance.

app-modules/booking/src/Filament/Resources/Bookings/Pages/ViewBooking.php

@@ -7,6 +7,7 @@ use Modules\Booking\Filament\Resources\Bookings\Actions\AssignDriverTableAction;
 use Modules\Booking\Filament\Resources\Bookings\Actions\CancelBookingTableAction;
 use Modules\Booking\Filament\Resources\Bookings\Actions\SetRemarkTableAction;
 use Modules\Booking\Filament\Resources\Bookings\BookingResource;
+use Modules\Payment\Filament\Actions\RefundBookingTableAction;
 
 class ViewBooking extends ViewRecord
 {
@@ -18,6 +19,7 @@ class ViewBooking extends ViewRecord
             AssignDriverTableAction::make(),
             SetRemarkTableAction::make(),
             CancelBookingTableAction::make(),
+            RefundBookingTableAction::make(),
         ];
     }
 }