fix: code-review warnings — deprecated APIs, debugPrint→Logger, unused import

lib/screens/settings_screen.dart

@@ -83,7 +83,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
                 style: TextStyle(color: MeloTheme.textSekundaer, fontSize: 12),
               ),
               value: _diagnose,
-              activeColor: MeloTheme.rot,
+              activeThumbColor: MeloTheme.rot,
               onChanged: (v) {
                 setState(() => _diagnose = v);
                 AppConfig.sendeDiagnosedaten = v;

lib/services/auth_service.dart

@@ -37,7 +37,7 @@ class AuthService {
         MeloLogger().zustand('auth_restored', {'user': _user});
       }
     } catch (e) {
-      debugPrint('AuthService init Fehler: $e');
+      MeloLogger().fehler('auth_init', e);
     }
     _initialisiert = true;
   }

lib/widgets/playlist_sheet.dart

@@ -233,7 +233,7 @@ class _PlaylistDetailState extends State<_PlaylistDetail> {
               ? const Center(child: Text('Playlist ist leer', style: TextStyle(fontSize: 12, color: MeloTheme.textSekundaer)))
               : ReorderableListView.builder(
                   itemCount: _songs.length,
-                  onReorder: (oldIndex, newIndex) async {
+                  onReorderItem: (oldIndex, newIndex) async {
                     if (newIndex > oldIndex) newIndex--;
                     setState(() {
                       final moved = _songs.removeAt(oldIndex);

lib/widgets/tag_auswahl_dialog.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import '../database/db_helper.dart';
 import '../models/tag.dart';
 import '../utils/farb_theme.dart';
-import '../services/melo_logger.dart';
+
 
 /// Dialog: Tags für einen Song zuweisen/entfernen
 class TagAuswahlDialog extends StatefulWidget {