Add functional Theme selection, with Provider for state management

frontend_splatournament_manager/lib/settings_page.dart

@@ -1,17 +1,14 @@
 import 'package:flutter/material.dart';
+import 'package:frontend_splatournament_manager/widgets/theme_selector_widget.dart';
 
 class SettingsPage extends StatefulWidget {
   const SettingsPage({super.key});
 
-  static const List<String> themes = ['System', 'Dark', 'Light'];
-
   @override
   State<SettingsPage> createState() => _SettingsPageState();
 }
 
 class _SettingsPageState extends State<SettingsPage> {
-  var dropDownValue = SettingsPage.themes[0];
-
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -19,23 +16,7 @@ class _SettingsPageState extends State<SettingsPage> {
       body: Center(
         child: Column(
           mainAxisSize: MainAxisSize.min,
-          children: [
-            Text("Settings"),
-            DropdownButton(
-              value: dropDownValue,
-              icon: Icon(Icons.color_lens),
-              items: SettingsPage.themes
-                  .map((e) => DropdownMenuItem(value: e, child: Text(e)))
-                  .toList(),
-              onChanged: (value){
-                if(value == null) return;
-                print(value);
-                setState(() {
-                  dropDownValue = value;
-                });
-              },
-            ),
-          ],
+          children: [ThemeSelectorWidget()],
         ),
       ),
     );