Add saved payout destination UX and service contracts (#54)

frontend/app/lib/destinations/paste.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/material.dart';
+
+import 'package:sxchnge_wallet/sxchnge_wallet.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class BankPasteDialog extends StatefulWidget {
+  const BankPasteDialog({super.key});
+  @override
+  State<BankPasteDialog> createState() => _BankPasteDialogState();
+}
+
+class _BankPasteDialogState extends State<BankPasteDialog> {
+  final text = TextEditingController();
+  BankPaste? result;
+  @override
+  void dispose() {
+    text.clear();
+    text.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l = AppLocalizations.of(context)!;
+    final labels = {
+      'firstName': l.dFirst,
+      'lastName': l.dLast,
+      'patronymic': l.dPatronymic,
+      'account': l.dAccount,
+      'bik': 'BIK',
+      'bank': l.dBankSearch,
+      'holder': l.dHolder,
+      'correspondent': l.dCorrespondent,
+    };
+    return AlertDialog(
+      title: Text(l.dPaste),
+      content: SizedBox(
+        width: 480,
+        child: SingleChildScrollView(
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text(l.dPasteHelp),
+              const SizedBox(height: 12),
+              TextField(
+                controller: text,
+                maxLines: 6,
+                decoration: InputDecoration(labelText: l.dBankDetails),
+                onChanged: (_) => setState(() => result = null),
+              ),
+              if (result != null) ...[
+                const SizedBox(height: 12),
+                if (result!.conflicts.isNotEmpty) Text(l.dPasteConflict),
+                for (final e in result!.values.entries)
+                  Text('${labels[e.key]}: ${e.value}'),
+              ],
+            ],
+          ),
+        ),
+      ),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.pop(context),
+          child: Text(l.wClose),
+        ),
+        FilledButton(
+          onPressed: result == null
+              ? () => setState(() => result = BankPaste.parse(text.text))
+              : result!.values.isEmpty
+              ? null
+              : () => Navigator.pop(context, result),
+          child: Text(result == null ? l.dPasteReview : l.dPasteApply),
+        ),
+      ],
+    );
+  }
+}