Include field library metadata in template exports

- Add fieldLibrary metadata to HTML template packages, including form fields, custom time formats, multi-select options, and anesthesia options.

- Restore imported template field metadata into local compatibility caches and the backend field library API when available.

- Preserve legacy JSON template import compatibility while keeping user-facing exports on HTML packages.

- Prevent template field saves from overwriting stored multi-select and anesthesia options with empty values.

- Update README, AGENTS, feature, requirement, design, module, progress, component, and testing docs for complete template export behavior.

- Extend template export tests to cover field library metadata round-tripping.

docs/testing.md

@@ -84,7 +84,7 @@ AI 第三方接口、讯飞语音上游 WebSocket、麦克风权限和真实视
 | 默认字段和 AI Provider | 已覆盖 | `defaultContent.test.ts` |
 | 打印导出入口 | 已覆盖 | `print.test.ts` |
 | 模板列表合并工具 | 已覆盖 | `templateList.test.ts`，防止新增模板被旧本地缓存覆盖。 |
-| 模板导入导出工具 | 已覆盖 | `templateExport.test.ts`，覆盖 HTML 模板包、HTML 回导、旧 JSON 导入兼容和文件名清理。 |
+| 模板导入导出工具 | 已覆盖 | `templateExport.test.ts`，覆盖 HTML 模板包、字段库元数据回导、旧 JSON 导入兼容和文件名清理。 |
 | 默认快捷登录 | 已覆盖 | `e2e/login.spec.ts` |
 | 报告权限 E2E | 已覆盖 | `e2e/report-permissions.spec.ts` |
 | 报告修订版本 E2E | 已覆盖 | `e2e/report-revision.spec.ts` |