Add Access group admin surfaces, booking soft deletes, refund crash fix

Access group (Filament):
- StaffResource: manage users with an admin-tier role, gated by manage_staff
- CustomerResource: read-only view of role-less users, gated by view_customers
- RoleResource: edit permissions per role (fixed role set), gated by manage_roles
- ManageAppSettings: tabbed General/Booking settings page that reads/writes
  real .env keys via new EnvFileWriter (no parallel DB settings table, so
  BookingService/config('booking.*') stay unchanged)
- Moved Access above Catalog in the nav group order
- New permissions: manage_staff, manage_roles, view_customers, manage_settings

Booking soft deletes:
- bookings.deleted_at + SoftDeletes on the Booking model
- BookingPolicy::delete (manage_bookings, cancelled/expired only) and
  ::restore (manage_bookings)
- DeleteBookingTableAction/RestoreBookingTableAction + TrashedFilter on
  BookingsTable, using authorize() so the policy is enforced at call time,
  not just cosmetically hidden

Refund crash fix:
- ProcessRefundAction passed a nullable $payment->booking into
  RefundBookingAction's non-nullable Booking param — a soft-deleted
  booking's payment reaching the refund picker was an uncaught TypeError.
  Excluded such payments from the picker and added a defensive guard.
- Same unguarded $event->payment->booking / $event->refund->payment->booking
  pattern fixed in the MarkBookingPaid/MarkBookingRefunded queued listeners.

289 tests passing.

app-modules/booking/src/Filament/Resources/Bookings/Actions/DeleteBookingTableAction.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Modules\Booking\Filament\Resources\Bookings\Actions;
+
+use Filament\Actions\DeleteAction;
+
+/**
+ * Soft-delete only (Booking uses SoftDeletes). `authorize('delete')` ties
+ * both the visible/hidden state AND the actual delete call itself to
+ * BookingPolicy::delete (manage_bookings + terminal status) — unlike
+ * visible()/disabled(), which are UI-only, authorize() is enforced when the
+ * action runs (Filament\Actions\Concerns\CanBeAuthorized). A booking that
+ * isn't cancelled/expired never shows this button at all, rather than a
+ * dead disabled one.
+ */
+class DeleteBookingTableAction
+{
+    public static function make(): DeleteAction
+    {
+        return DeleteAction::make()
+            ->authorize('delete');
+    }
+}