Add local data store adapter layer and Hive scaffold

lib/features/local/storage/local_data_store.dart

@@ -0,0 +1,19 @@
+/// Raw local state payload and associated schema version.
+class LocalDataRecord {
+  const LocalDataRecord({required this.rawState, required this.schemaVersion});
+
+  final String rawState;
+  final int schemaVersion;
+}
+
+/// Persistence boundary for local app state.
+abstract interface class LocalDataStore {
+  /// Reads latest persisted state payload.
+  Future<LocalDataRecord?> read();
+
+  /// Writes state payload and schema version.
+  Future<void> write({required String rawState, required int schemaVersion});
+
+  /// Clears persisted state payload.
+  Future<void> clear();
+}