feat(auth): Enhance logout flow with comprehensive data clearing

lib/core/services/optimized_storage_service.dart

@@ -395,11 +395,15 @@ class OptimizedStorageService {
   // ---------------------------------------------------------------------------
   // Batch operations
   // ---------------------------------------------------------------------------
+  /// Clear all authentication-related data including credentials, tokens,
+  /// server configurations, and custom headers
   Future<void> clearAuthData() async {
     await Future.wait([
       deleteAuthToken(),
       deleteSavedCredentials(),
       _preferencesBox.delete(_activeServerIdKey),
+      // Clear server configurations (which include custom headers)
+      _secureCredentialStorage.clearAll(),
     ]);
 
     _cache.removeWhere(
@@ -416,7 +420,7 @@ class OptimizedStorageService {
     );
 
     DebugLogger.log(
-      'Auth data cleared in batch operation',
+      'Auth data cleared in batch operation (including server configs and custom headers)',
       scope: 'storage/optimized',
     );
   }

lib/core/services/secure_credential_storage.dart

@@ -280,11 +280,12 @@ class SecureCredentialStorage {
     }
   }
 
-  /// Clear all secure data
+  /// Clear all secure data including credentials, tokens, and server configurations
+  /// (which contain custom headers)
   Future<void> clearAll() async {
     try {
       await _secureStorage.deleteAll();
-      DebugLogger.storage('clear-ok', scope: 'credentials');
+      DebugLogger.storage('clear-ok (all secure data including server configs with custom headers)', scope: 'credentials');
     } catch (e) {
       DebugLogger.error('clear-failed', scope: 'credentials', error: e);
     }