delete CloudKit and added BalanceFlutter

BalanceFlutter/lib/services/storage.dart

@@ -0,0 +1,58 @@
+import 'package:sembast/sembast.dart';
+
+import 'storage_native.dart'
+    if (dart.library.js_interop) 'storage_web.dart'
+    as platform;
+
+/// A single transaction replaces the complete ledger, pending changes and cursor.
+abstract class SnapshotStorage {
+  Future<Map<String, dynamic>?> read(String key);
+  Future<void> write(String key, Map<String, dynamic> value);
+  Future<void> close();
+}
+
+/// Connections are opened lazily and closed after every operation, so another
+/// Flutter engine never reads through an old Sembast in-memory cache. Android
+/// callers serialize complete operations with the shared native store lock.
+class LedgerStorage implements SnapshotStorage {
+  LedgerStorage._();
+  final _store = stringMapStoreFactory.store('snapshots');
+  static Future<LedgerStorage> open() async => LedgerStorage._();
+  @override
+  Future<Map<String, dynamic>?> read(String key) async {
+    final db = await platform.openLedgerDatabase();
+    try {
+      return await _store.record(key).get(db);
+    } finally {
+      await db.close();
+    }
+  }
+
+  @override
+  Future<void> write(String key, Map<String, dynamic> value) async {
+    final db = await platform.openLedgerDatabase();
+    try {
+      await db.transaction((txn) async {
+        await _store.record(key).put(txn, value);
+      });
+    } finally {
+      await db.close();
+    }
+  }
+
+  @override
+  Future<void> close() async {}
+}
+
+class MemorySnapshotStorage implements SnapshotStorage {
+  final Map<String, Map<String, dynamic>> values = {};
+  @override
+  Future<Map<String, dynamic>?> read(String key) async => values[key];
+  @override
+  Future<void> write(String key, Map<String, dynamic> value) async {
+    values[key] = value;
+  }
+
+  @override
+  Future<void> close() async {}
+}