Fix Exception

- Replace synchronous Isar writes with async transactions in `AboutScreen`
- Make `AppLogger.init()` and `dispose()` fully async and guarded with `_busy`
- Remove `StreamController` queue and write directly to the IOSink
- Prevent double‑initialization and race conditions using `_initialized` + `_busy`
- Update log toggle handler to await logger init/dispose for consistency

Fix following Exception when disabling and re-enabling logger:

```
Exception has occurred.
StateError (Bad state: Stream has already been listened to.)
```

lib/modules/more/about/about_screen.dart

@@ -86,18 +86,18 @@ class AboutScreen extends ConsumerWidget {
                       SwitchListTile(
                         title: Text(l10n.logs_on),
                         value: enableLogs,
-                        onChanged: (value) {
-                          isar.writeTxnSync(() {
-                            final settings = isar.settings.getSync(227);
-                            isar.settings.putSync(
+                        onChanged: (value) async {
+                          await isar.writeTxn(() async {
+                            final settings = await isar.settings.get(227);
+                            await isar.settings.put(
                               settings!..enableLogs = value,
                             );
                           });
                           ref.invalidate(logsStateProvider);
                           if (value) {
-                            AppLogger.init();
+                            await AppLogger.init();
                           } else {
-                            AppLogger.dispose();
+                            await AppLogger.dispose();
                           }
                         },
                       ),

lib/utils/log/logger.dart

@@ -6,39 +6,41 @@ import 'package:mangayomi/providers/storage_provider.dart';
 import 'package:path/path.dart' as path;
 
 class AppLogger {
-  static final _logQueue = StreamController<String>();
-  static late File _logFile;
-  static late IOSink _sink;
+  static File? _logFile;
+  static IOSink? _sink;
   static bool _initialized = false;
+  static bool _busy = false;
 
   /// Initialize the logger
   static Future<void> init() async {
-    final enabled = isar.settings.getSync(227)?.enableLogs ?? false;
-    if (!enabled) return;
-    final storage = StorageProvider();
-    final directory = await storage.getDefaultDirectory();
-    _logFile = File(path.join(directory!.path, 'logs.txt'));
+    if (_initialized || _busy) return;
+    _busy = true;
+    try {
+      final enabled = (await isar.settings.get(227))?.enableLogs ?? false;
+      if (!enabled) return;
+      final storage = StorageProvider();
+      final directory = await storage.getDefaultDirectory();
+      _logFile = File(path.join(directory!.path, 'logs.txt'));
 
-    if (await _logFile.exists() && await _logFile.length() > 100 * 1024) {
-      await _logFile.delete();
+      if (await _logFile!.exists() && await _logFile!.length() > 100 * 1024) {
+        await _logFile!.delete();
+      }
+
+      if (!await _logFile!.exists()) {
+        await _logFile!.create(recursive: true);
+      }
+
+      _sink = _logFile!.openWrite(mode: FileMode.append);
+      _initialized = true;
+
+      log('\n\nLogger initialized\n\n');
+    } finally {
+      _busy = false;
     }
-
-    if (!await _logFile.exists()) {
-      await _logFile.create(recursive: true);
-    }
-
-    _sink = _logFile.openWrite(mode: FileMode.append);
-    _initialized = true;
-
-    _logQueue.stream.listen((log) {
-      _sink.writeln(log);
-    });
-
-    log('\n\nLogger initialized\n\n');
   }
 
   static void log(String message, {LogLevel logLevel = LogLevel.info}) {
-    if (!_initialized) return;
+    if (!_initialized || _sink == null) return;
 
     final now = DateTime.now();
     final timestamp =
@@ -46,15 +48,21 @@ class AppLogger {
         '${now.hour.toString().padLeft(2, '0')}:${now.minute.toString().padLeft(2, '0')}:${now.second.toString().padLeft(2, '0')}';
 
     final logMessage = '[$timestamp][${logLevel.toString()}] $message';
-    _logQueue.add(logMessage);
+    _sink!.writeln(logMessage);
   }
 
   static Future<void> dispose() async {
-    if (!_initialized) return;
-    await _logQueue.close();
-    await _sink.flush();
-    await _sink.close();
-    _initialized = false;
+    if (!_initialized || _busy) return;
+    _busy = true;
+    try {
+      await _sink?.flush();
+      await _sink?.close();
+      _sink = null;
+      _logFile = null;
+      _initialized = false;
+    } finally {
+      _busy = false;
+    }
   }
 }