Remove Wyre buy-provider integration (shut down 2023)

Delete the WyreBuyProvider + WyreOrderProviderAdapter source files,
strip imports and call sites from buy/order view models and the
buy webview, force isBitcoinBuyEnabled = false in di.dart, and drop
the three wyreSecretKey/wyreApiKey/wyreAccountId entries from
tool/utils/secret_key.dart.

BuyProviderDescription.wyre (raw: 0) is kept as a no-op legacy entry
so any old Hive-persisted order with that raw value still deserializes
without throwing. Don't wire it back to UI/services.

lib/src/screens/buy/buy_webview_page.dart

@@ -1,6 +1,5 @@
 import 'dart:async';
 import 'package:hash_wallet/buy/moonpay/moonpay_provider.dart';
-import 'package:hash_wallet/buy/wyre/wyre_buy_provider.dart';
 import 'package:hash_wallet/generated/i18n.dart';
 import 'package:hash_wallet/src/screens/base_page.dart';
 import 'package:hash_wallet/store/dashboard/orders_store.dart';
@@ -54,10 +53,6 @@ class BuyWebViewPageBodyState extends State<BuyWebViewPageBody> {
     _isSaving = false;
     widget.ordersStore.orderId = '';
 
-    if (widget.buyViewModel.selectedProvider is WyreBuyProvider) {
-      _saveOrder(keyword: 'completed', splitSymbol: '/');
-    }
-
     if (widget.buyViewModel.selectedProvider is MoonPayProvider) {
       _saveOrder(keyword: 'transactionId', splitSymbol: '=');
     }