Add reusable HTML template export

- Add template export utilities for standard JSON packages and standalone HTML template packages.

- Make the top-level JSON export use the standard surclaw template package format so it can be imported again.

- Add an HTML template package export that embeds A4/print styling and template metadata for visual preview and round-trip import.

- Extend template import to accept both JSON and HTML template package files while keeping old raw template JSON compatible.

- Add tests for package creation, HTML round-trip import, legacy JSON import, and file name cleanup.

- Update template management, feature, progress, testing, and AGENTS documentation for the new export formats.

AGENTS.md

@@ -350,6 +350,7 @@ PostgreSQL 数据模型。当前覆盖 `Tenant`、`Department`、`User`、`UserS
 - 后端报告 schema 区分草稿和完成状态，草稿可暂缺患者姓名/住院号，完成报告必须填写
 - 后端模板 DTO 和权限资源映射
 - 模板列表合并工具，防止新增模板被旧 `localStorage.templates` 覆盖
+- 模板导入导出工具，覆盖 JSON/HTML 模板包生成、回导和旧 JSON 兼容
 - 后端用户 DTO 和部门模板授权映射
 - 后端系统设置 schema 校验
 - 后端 AI 入参和讯飞语音代理帧处理