feat(SharePoster): 使用html-to-image生成海报并优化资源加载

重构海报生成逻辑，使用html-to-image替代canvas手动绘制，提升生成稳定性
添加生成中状态提示，优先使用base64资源避免跨域问题
优化封面和二维码加载逻辑，移除冗余canvas代码

@@ -34,6 +34,7 @@
     "@vue-office/pptx": "^1.0.1",
     "browser-md5-file": "^1.1.1",
     "dayjs": "^1.11.13",
+    "html-to-image": "^1.11.13",
     "html2canvas": "^1.4.1",
     "lodash": "^4.17.21",
     "pdf-vue3": "^1.0.12",

@@ -47,6 +47,9 @@ importers:
       dayjs:
         specifier: ^1.11.13
         version: 1.11.19
+      html-to-image:
+        specifier: ^1.11.13
+        version: 1.11.13
       html2canvas:
         specifier: ^1.4.1
         version: 1.4.1
@@ -1167,6 +1170,9 @@ packages:
     resolution: {integrity: sha512-0hJU9SCPvmMzIBdZFqNPXWa6dqh7WdH0cII9y+CyS8rG3nL48Bclra9HmKhVVUHyPWNH5Y7xDwAB7bfgSjkUMQ==}
     engines: {node: '>= 0.4'}
 
+  html-to-image@1.11.13:
+    resolution: {integrity: sha512-cuOPoI7WApyhBElTTb9oqsawRvZ0rHhaHwghRLlTuffoD1B2aDemlCruLeZrUIIdvG7gs9xeELEPm6PhuASqrg==}
+
   html2canvas@1.4.1:
     resolution: {integrity: sha512-fPU6BHNpsyIhr8yyMpTLLxAbkaK8ArIBcmZIRiBLiDhjeqvXolaEmDGmELFuX9I4xDcaKKcJl+TKZLqruBbmWA==}
     engines: {node: '>=8.0.0'}
@@ -3036,6 +3042,8 @@ snapshots:
     dependencies:
       function-bind: 1.1.2
 
+  html-to-image@1.11.13: {}
+
   html2canvas@1.4.1:
     dependencies:
       css-line-break: 2.1.0