feat(typesetting): 页面品牌标识 - 数据链路+渲染函数+分页修正

- Post.php: phoneImage()传递siteName/siteLogo到模板
- phone_image.html: postData增加siteName/siteLogo字段
- phone-image.js: 新增generateBrandHeader()+preloadBrandLogo()
- phone-image.js: 3个页面生成函数调用品牌头部
- phone-image.js: contentAreaHeight扣减BRAND_HEADER_HEIGHT(36px)
- logo预转base64规避html2canvas CORS，过滤默认头像

app/admin/controller/Post.php

@@ -380,6 +380,8 @@ class Post extends Common
         View::assign('layoutContentHtml', $layoutContentHtml);
         View::assign('layoutConfig', $layoutConfig);
         View::assign('lastOutputId', $postOutput ? $postOutput->id : 0);
+        View::assign('siteName', \app\common\tools\Site::name() ?? '');
+        View::assign('siteLogo', \app\common\tools\Site::logo() ?? '');
         return View::fetch();
     }