fix(Student): 修复iframe内容宽度和高度问题

设置iframe内容宽度为100vw，高度为100vh以确保内容正确显示

src/views/Student/index.vue

@@ -1906,6 +1906,8 @@ const handleHomeworkSubmit = async () => {
           try {
             const a = iframeBody.getElementsByTagName('img')
             const b = iframeBody.getElementsByTagName('video')
+            iframeBody.style.width = '100vw'
+            iframeBody.style.height = '100vh'
             for (let i = 0;i < a.length;i++) {
               a[i].crossOrigin = 'anonymous'
             }
@@ -2090,6 +2092,8 @@ const handleHomeworkSubmit = async () => {
             iframeElement.contentWindow.document &&
             iframeElement.contentWindow.document.body
         ) {
+          iframeElement.contentWindow.document.body.style.width = '100vw'
+          iframeElement.contentWindow.document.body.style.height = '100vh'
           try {
             isSubmitting.value = true