新增二维码加载状态管理，优化二维码获取逻辑，支持提前获取二维码并清理定时器，提升用户体验

src/composables/usePlayState.js

@@ -34,7 +34,10 @@ export function usePlayState() {
     qrRetryDelay: 2000,
     qrError: null,
     mecmachineId: null,
-    machineId: null
+    machineId: null,
+    qrCreatedAt: null,
+    qrExpireAt: null,
+    qrDelayTimeoutId: null
   })
 
   const initializePage = async () => {
@@ -206,6 +209,12 @@ export function usePlayState() {
     state.assets = data.assets
     state.mecmachineId = data.mecmachineId || null
     state.machineId = data.machineId || null
+    if (data.qrCreatedAt) {
+      state.qrCreatedAt = data.qrCreatedAt
+    }
+    if (data.qrExpireAt) {
+      state.qrExpireAt = data.qrExpireAt
+    }
     
     if (data.totalPoints) {
       state.totalPoints = data.totalPoints