TF-3171 Fix duplicate signature button on Composer view changed

lib/features/composer/presentation/composer_controller.dart

@@ -1452,6 +1452,11 @@ class ComposerController extends BaseController with DragDropFileMixin implement
     try {
       if (emailContent == null) return;
       final emailDocument = parse(emailContent);
+
+      final existedSignatureButton = emailDocument.querySelector(
+        'button.tmail-signature-button');
+      if (existedSignatureButton != null) return;
+      
       final signature = emailDocument.querySelector('div.tmail-signature');
       if (signature == null) return;
       _restoringSignatureButton = true;
@@ -1935,6 +1940,7 @@ class ComposerController extends BaseController with DragDropFileMixin implement
 
 
   void handleInitHtmlEditorWeb(String initContent) async {
+    if (_isEmailBodyLoaded) return;
     log('ComposerController::handleInitHtmlEditorWeb:');
     _isEmailBodyLoaded = true;
     richTextWebController?.editorController.setFullScreen();