style(Student): 统一字符串引号格式并优化iframe样式设置

将单引号统一为双引号，并优化iframe元素的样式设置方式，使用cssText进行批量操作

src/views/Student/index.vue

@@ -1898,7 +1898,7 @@ const handleHomeworkSubmit = async () => {
             })
 
             iframeBody = iframeElement.contentWindow.document.body as HTMLElement
-            iframehtml = iframeElement.contentWindow.document.getElementsByTagName("html")[0] as HTMLElement
+            iframehtml = iframeElement.contentWindow.document.getElementsByTagName('html')[0] as HTMLElement
           }
           else {
             message.error(lang.ssFailedGetIframeBody)
@@ -1908,7 +1908,7 @@ const handleHomeworkSubmit = async () => {
           try {
             const a = iframeBody.getElementsByTagName('img')
             const b = iframeBody.getElementsByTagName('video')
-            //const c = iframeBody.getElementsByTagName('canvas')
+            // const c = iframeBody.getElementsByTagName('canvas')
             iframeBody.style.cssText += 'width:100%;height:100%;position:absolute;top:0;left:0;'
             iframehtml.style.cssText += 'width:100%;height:100%;position:absolute;top:0;left:0;'
             for (let i = 0;i < a.length;i++) {
@@ -2096,8 +2096,8 @@ const handleHomeworkSubmit = async () => {
             iframeElement.contentWindow.document &&
             iframeElement.contentWindow.document.body
         ) {
-          iframeElement.contentWindow.document.body.style.width = '100vw'
-          iframeElement.contentWindow.document.body.style.height = '100vh'
+          iframeElement.contentWindow.document.body.style.cssText += 'width:100%;height:100%;position:absolute;top:0;left:0;'
+          iframeElement.contentWindow.document.getElementsByTagName('html')[0].style.cssText += 'width:100%;height:100%;position:absolute;top:0;left:0;'
           try {
             isSubmitting.value = true