Complete refactor to clean up project

lib/core/services/storage_service.dart

@@ -0,0 +1,119 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:hive/hive.dart';
+import 'package:sheetless/core/models/change.dart';
+import 'package:sheetless/core/models/config.dart';
+
+/// Keys for secure storage (credentials and tokens).
+enum SecureStorageKey { url, jwt, email }
+
+/// Service for managing local storage operations.
+///
+/// Uses [FlutterSecureStorage] for sensitive data (credentials, tokens)
+/// and [Hive] for general app data (config, sheet access times, change queue).
+class StorageService {
+  // Hive box names
+  static const String _sheetAccessTimesBox = 'sheetAccessTimes';
+  static const String _configBox = 'config';
+  static const String _changeQueueBox = 'changeQueue';
+
+  late final FlutterSecureStorage _secureStorage;
+
+  StorageService() {
+    _secureStorage = FlutterSecureStorage(
+      aOptions: const AndroidOptions(encryptedSharedPreferences: true),
+    );
+  }
+
+  // ---------------------------------------------------------------------------
+  // Secure Storage (Credentials & Tokens)
+  // ---------------------------------------------------------------------------
+
+  /// Reads a value from secure storage.
+  Future<String?> readSecure(SecureStorageKey key) {
+    return _secureStorage.read(key: key.name);
+  }
+
+  /// Writes a value to secure storage.
+  ///
+  /// Pass `null` to delete the key.
+  Future<void> writeSecure(SecureStorageKey key, String? value) {
+    return _secureStorage.write(key: key.name, value: value);
+  }
+
+  /// Clears the JWT token from secure storage.
+  Future<void> clearToken() {
+    return writeSecure(SecureStorageKey.jwt, null);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Config
+  // ---------------------------------------------------------------------------
+
+  /// Reads the app configuration from storage.
+  Future<Config> readConfig() async {
+    final box = await Hive.openBox(_configBox);
+    return Config(
+      twoPageMode: box.get(Config.keyTwoPageMode) ?? false,
+      fullscreen: box.get(Config.keyFullscreen) ?? false,
+    );
+  }
+
+  /// Writes the app configuration to storage.
+  Future<void> writeConfig(Config config) async {
+    final box = await Hive.openBox(_configBox);
+    await box.put(Config.keyTwoPageMode, config.twoPageMode);
+    await box.put(Config.keyFullscreen, config.fullscreen);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Sheet Access Times (for sorting by recency)
+  // ---------------------------------------------------------------------------
+
+  /// Reads all sheet access times.
+  ///
+  /// Returns a map of sheet UUID to last access time.
+  Future<Map<String, DateTime>> readSheetAccessTimes() async {
+    final box = await Hive.openBox(_sheetAccessTimesBox);
+    return box.toMap().map(
+      (key, value) => MapEntry(key as String, DateTime.parse(value as String)),
+    );
+  }
+
+  /// Records when a sheet was last accessed.
+  Future<void> writeSheetAccessTime(String uuid, DateTime datetime) async {
+    final box = await Hive.openBox(_sheetAccessTimesBox);
+    await box.put(uuid, datetime.toIso8601String());
+  }
+
+  // ---------------------------------------------------------------------------
+  // Change Queue (Offline Sync)
+  // ---------------------------------------------------------------------------
+
+  /// Adds a change to the offline queue.
+  Future<void> writeChange(Change change) async {
+    final box = await Hive.openBox(_changeQueueBox);
+    await box.add(change.toMap());
+  }
+
+  /// Reads all pending changes from the queue.
+  Future<ChangeQueue> readChangeQueue() async {
+    final box = await Hive.openBox(_changeQueueBox);
+    final queue = ChangeQueue();
+
+    for (final map in box.values) {
+      queue.addChange(Change.fromMap(map as Map<dynamic, dynamic>));
+    }
+
+    return queue;
+  }
+
+  /// Removes the oldest change from the queue.
+  ///
+  /// Call this after successfully syncing a change to the server.
+  Future<void> deleteOldestChange() async {
+    final box = await Hive.openBox(_changeQueueBox);
+    if (box.isNotEmpty) {
+      await box.deleteAt(0);
+    }
+  }
+}