fix(student page): 调整iframe刷新延迟时间从50ms到1000ms

延长刷新等待时间，避免因刷新过快导致iframe加载未完成就被重置，提升页面刷新稳定性

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`)
-        }, 50)
+        }, 1000)
         refreshedCount++
       }
     }