Complete refactor to clean up project

lib/core/models/config.dart

@@ -0,0 +1,37 @@
+/// Application configuration model.
+///
+/// Stores user preferences that are persisted across sessions,
+/// such as display mode and fullscreen settings.
+class Config {
+  /// Storage keys for persistence
+  static const String keyTwoPageMode = 'twoPageMode';
+  static const String keyFullscreen = 'fullscreen';
+
+  /// Whether to display two pages side-by-side (for tablets/landscape).
+  bool twoPageMode;
+
+  /// Whether the app is in fullscreen mode.
+  bool fullscreen;
+
+  Config({
+    required this.twoPageMode,
+    required this.fullscreen,
+  });
+
+  /// Creates a default configuration with all options disabled.
+  factory Config.defaultConfig() => Config(
+        twoPageMode: false,
+        fullscreen: false,
+      );
+
+  /// Creates a copy of this config with optional overrides.
+  Config copyWith({
+    bool? twoPageMode,
+    bool? fullscreen,
+  }) {
+    return Config(
+      twoPageMode: twoPageMode ?? this.twoPageMode,
+      fullscreen: fullscreen ?? this.fullscreen,
+    );
+  }
+}