fix(PosterBuilder): 替换废弃的getSystemInfoSync并优化downImage类型

使用Taro.getWindowInfo()替代已废弃的getSystemInfoSync，并添加错误处理
为downImage函数添加类型声明，明确返回Promise<string>

@@ -104,9 +104,16 @@ export function mapHttpToHttps(rawUrl) {
  * @returns { number } factor 单位转换系数 1rpx = factor * px
  */
 export const getFactor = () => {
-  const sysInfo = Taro.getSystemInfoSync();
-  const { screenWidth } = sysInfo;
-  return screenWidth / 750;
+  try {
+    // 使用新的API替代已废弃的getSystemInfoSync
+    const windowInfo = Taro.getWindowInfo();
+    const { screenWidth } = windowInfo;
+    return screenWidth / 750;
+  } catch (error) {
+    console.warn('获取窗口信息失败，使用默认转换系数:', error);
+    // 如果新API不可用，使用默认值（基于iPhone6的屏幕宽度375px）
+    return 375 / 750;
+  }
 };
 
 /**
@@ -133,8 +140,8 @@ export const toRpx = (px, factor = getFactor()) =>
  * @param { number } retryCount - 重试次数
  * @returns  { Promise }
  */
-export function downImage(url, retryCount = 2) {
-  return new Promise((resolve, reject) => {
+export function downImage(url: string, retryCount = 2): Promise<string> {
+  return new Promise<string>((resolve, reject) => {
     // eslint-disable-next-line no-undef
     if (/^http/.test(url) && !new RegExp(wx.env.USER_DATA_PATH).test(url)) {
       // wx.env.USER_DATA_PATH 文件系统中的用户目录路径
@@ -144,7 +151,7 @@ export function downImage(url, retryCount = 2) {
           timeout: 10000, // 设置10秒超时
           success: (res) => {
             if (res.statusCode === 200) {
-              resolve(res.tempFilePath);
+              resolve(res.tempFilePath as string);
             } else {
               // console.log('下载失败', res);
               if (attempt < retryCount) {
@@ -167,7 +174,7 @@ export function downImage(url, retryCount = 2) {
                     timeout: 10000,
                     success: (res) => {
                       if (res.statusCode === 200) {
-                        resolve(res.tempFilePath);
+                        resolve(res.tempFilePath as string);
                       } else {
                         reject(res);
                       }
@@ -195,7 +202,7 @@ export function downImage(url, retryCount = 2) {
       };
       attemptDownload();
     } else {
-      resolve(url); // 支持本地地址
+      resolve(url as string); // 支持本地地址
     }
   });
 }