Move to Flutter 3.47, use the improvements that come with this (#64)

Reviewed-on: #64

lib/models/settings.dart

@@ -1,15 +1,17 @@
-import "package:flutter/material.dart";
+import "package:material_ui/material_ui.dart";
 import "package:freezed_annotation/freezed_annotation.dart";
+
 part "settings.freezed.dart";
 part "settings.g.dart";
 
-@freezed
-abstract class Settings with _$Settings {
-  const factory Settings({
-    @Default(ThemeMode.system) ThemeMode theme,
-    @Default(true) bool useDynamicTheming,
-    @Default(false) bool linuxMobileMode,
-  }) = _Settings;
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const Settings({
+  final ThemeMode theme = ThemeMode.system,
+  final bool useDynamicTheming = true,
+  final bool linuxMobileMode = false,
+}) with _$Settings {
+  Map<String, Object?> toJson() => _$SettingsToJson(this);
 
   factory Settings.fromJson(Map<String, Object?> json) =>
       _$SettingsFromJson(json);