Refactor: Move theme management to ThemeController, add LocaleController and ScaleController for improved UI customization, and update related imports.

finlog_app/app/lib/core/ui/controller/locale_controller.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+import 'package:fluttery/fluttery.dart';
+import 'package:fluttery/preferences.dart';
+
+/// Controls the current app language (system, de, en, ...).
+/// Loads the locale from Preferences or falls back to system default.
+class LocaleController extends ChangeNotifier {
+  final Preferences _prefs;
+
+  LocaleController() : _prefs = App.service<Preferences>();
+
+  static const _key = 'language';
+
+  String _current = 'system';
+
+  Future<void> init() async {
+    final saved = await _prefs.getString(_key);
+    _current = saved ?? 'system';
+    notifyListeners();
+  }
+
+  void setLanguage(String lang) {
+    _current = lang;
+    notifyListeners();
+    _prefs.setString(_key, lang);
+  }
+
+  /// Returns the actual Locale or null = system.
+  Locale? get locale {
+    switch (_current) {
+      case 'de':
+        return const Locale('de');
+      case 'en':
+        return const Locale('en');
+      case 'system':
+      default:
+        return null;
+    }
+  }
+
+  String get language => _current;
+}

finlog_app/app/lib/core/ui/controller/scale_controller.dart

@@ -0,0 +1,47 @@
+import 'package:flutter/material.dart';
+import 'package:fluttery/fluttery.dart';
+import 'package:fluttery/preferences.dart';
+
+/// Controls the current text scale (system, small, medium, large).
+/// Loads the value from Preferences or falls back to system default.
+class ScaleController extends ChangeNotifier {
+  final Preferences _prefs;
+
+  ScaleController() : _prefs = App.service<Preferences>();
+
+  static const _key = 'textScale';
+
+  /// supported sizes
+  static const Map<String, double> _factors = {
+    'system': 1.0,
+    'small': 0.9,
+    'medium': 1.1,
+    'large': 1.25,
+  };
+
+  String _current = 'system';
+
+  /// Loads text scale from Preferences.
+  Future<void> init() async {
+    final saved = await _prefs.getString(_key);
+    _current = saved ?? 'system';
+    if (!_factors.containsKey(_current)) {
+      _current = 'system';
+    }
+    notifyListeners();
+  }
+
+  /// Set text scale and persist.
+  void setScale(String scale) {
+    if (!_factors.containsKey(scale)) return;
+    _current = scale;
+    notifyListeners();
+    _prefs.setString(_key, scale);
+  }
+
+  /// get current factor (e.g. for MediaQuery.textScaler)
+  double get factor => _factors[_current]!;
+
+  /// get current string (system/small/medium/large)
+  String get scale => _current;
+}

finlog_app/app/lib/core/ui/controller/theme.dart

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+import 'package:flutter/material.dart';
+import 'package:fluttery/fluttery.dart';
+import 'package:fluttery/preferences.dart';
+
+/// Controls the current theme of the application.
+/// Loads the theme from Preferences or falls back to system default.
+class ThemeController extends ChangeNotifier {
+  final Preferences _prefs;
+
+  /// themeMode (system, dark or white)
+  ThemeMode _themeMode = ThemeMode.system;
+
+  /// Constructor
+  ThemeController() : _prefs = App.service<Preferences>();
+
+  /// Loads theme from Preferences (or defaults to system).
+  Future<void> init() async {
+    final saved = await _prefs.getString('theme');
+    if (saved == null) {
+      _themeMode = ThemeMode.system;
+    } else {
+      _themeMode = _fromString(saved);
+    }
+    notifyListeners();
+  }
+
+  /// Sets theme and persists it in Preferences.
+  void setTheme(ThemeMode mode) {
+    _themeMode = mode;
+    notifyListeners();
+    _prefs.setString('theme', mode.name);
+  }
+
+  ThemeMode _fromString(String value) {
+    switch (value) {
+      case 'light':
+        return ThemeMode.light;
+      case 'dark':
+        return ThemeMode.dark;
+      case 'system':
+      default:
+        return ThemeMode.system;
+    }
+  }
+
+  /// get current ThemeMode
+  ThemeMode get themeMode => _themeMode;
+}