fix(student page): 调整iframe刷新延迟为5秒

将原本1秒的刷新延迟调整为5秒，避免刷新过快导致的异常问题

src/views/Student/index.vue

@@ -2593,7 +2593,7 @@ const handleRefreshPage = () => {
         setTimeout(() => {
           iframe.srcdoc = originalSrcdoc
           console.log(`iframe ${i + 1} (srcdoc) 刷新完成`)
-        }, 1000)
+        }, 5000)
         refreshedCount++
       }
     }