TF-3911 Remove window event listeners to prevent memory leaks in Email View

core/lib/utils/html/html_interaction.dart

@@ -286,7 +286,13 @@ class HtmlInteraction {
       }, {
         passive: false,
       });
-      window.addEventListener('keydown', function(e) {
+      window.addEventListener('keydown', disableZoomControl);
+      
+      window.addEventListener('pagehide', (event) => {
+        window.removeEventListener('keydown', disableZoomControl);
+      });
+      
+      function disableZoomControl(event) {
         if (event.metaKey || event.ctrlKey) {
           switch (event.key) {
             case '=':
@@ -295,7 +301,7 @@ class HtmlInteraction {
               break;
           }
         }
-      });
+      }
     </script>
   ''';
 
@@ -381,7 +387,13 @@ class HtmlInteraction {
 
   static String scriptHandleIframeKeyboardListener(String viewId) => '''
     <script type="text/javascript">
-      window.addEventListener('keydown', function (event) {
+      window.addEventListener('keydown', handleIframeKeydown);
+      
+      window.addEventListener('pagehide', (event) => {
+        window.removeEventListener('keydown', handleIframeKeydown);
+      });
+      
+      function handleIframeKeydown(event) {
         const payload = {
           view: '$viewId',
           type: 'toDart: iframeKeydown',
@@ -390,7 +402,7 @@ class HtmlInteraction {
           shift: event.shiftKey
         };
         window.parent.postMessage(JSON.stringify(payload), "*");
-      });
+      }
     </script>
   ''';
 }