feat: Enhance documentation on layering, object naming conventions, and API design

- Added object naming conventions (PO/DAO/BO/DTO/VO) in 02-layering.md to clarify terminology and usage within the team.
- Updated 06-api-design.md to include MapStruct for DTO and entity conversion, providing examples and configuration details.
- Expanded 07-config-governance.md with local development instructions and strategies for running without K8s, including two recommended approaches.
- Included K8s probe configuration details in 08-observability.md for liveness and readiness checks.
- Clarified CI/CD processes in 09-build-deploy.md, detailing environment distinctions and deployment strategies for local, Dev, UAT, and Prod.
- Introduced ArchUnit for architectural testing in 10-testing.md, ensuring adherence to defined layering rules and coverage verification with Jacoco.

backend/06-api-design.md

@@ -96,6 +96,37 @@ data class StoreResponse(
 
 Controller 不直接返回 `StoreEntity`，而是转换成 `StoreResponse`——即使当前字段一模一样，也统一走这层转换，避免以后 entity 加了内部字段（比如某个只有 `infrastructure` 层需要的标记位）被不小心带出去。
 
+## DTO 与 entity 的转换：用 MapStruct
+
+转换代码用 [MapStruct](https://mapstruct.org/) 自动生成，不手写。字段名一致的直接映射，不一致的用 `@Mapping` 指定，编译期生成实现类，没有反射开销，字段漏映射编译期就能发现。
+
+```groovy
+// build.gradle（Kotlin 项目用 kapt 做注解处理）
+plugins {
+    id 'org.jetbrains.kotlin.kapt'
+}
+
+dependencies {
+    implementation 'org.mapstruct:mapstruct:1.6.3'
+    kapt 'org.mapstruct:mapstruct-processor:1.6.3'
+}
+```
+
+```kotlin
+// api/mapper/StoreMapper.kt
+@Mapper(componentModel = "spring")
+interface StoreMapper {
+    fun toResponse(entity: StoreEntity): StoreResponse
+
+    @Mapping(target = "displayName", source = "name")
+    fun toSummary(entity: StoreEntity): StoreSummaryResponse // 字段名不一致时用 @Mapping 指定
+
+    fun toResponseList(entities: List<StoreEntity>): List<StoreResponse>
+}
+```
+
+`componentModel = "spring"` 让 MapStruct 生成的实现类自动注册成 Spring bean，直接在 `application` 层注入 `StoreMapper` 使用，不用手动 `new`。
+
 ## 关键规则
 
 - Controller 不直接返回 entity，统一走 `Xxx*Response` DTO，避免持久层字段变更影响 API 契约。
@@ -115,7 +146,6 @@ Controller 不直接返回 `StoreEntity`，而是转换成 `StoreResponse`——
 
 ## 待补充
 
-- DTO 与 entity 的转换方式（MapStruct 还是手写 mapper，模块变多之后再评估）。
 - 分页/排序参数的统一约定。
 - 错误码表（按 domain 分段还是全局统一编码）。
 
@@ -124,3 +154,4 @@ Controller 不直接返回 `StoreEntity`，而是转换成 `StoreResponse`——
 - [springdoc-openapi](https://springdoc.org/)
 - [Spring 官方 Bean Validation 指南](https://docs.spring.io/spring-framework/reference/core/validation/beanvalidation.html)
 - [Microsoft REST API 设计指南](https://github.com/microsoft/api-guidelines)
+- [MapStruct 官方文档](https://mapstruct.org/documentation/stable/reference/html/)