docs(story012.004): 更新故事状态为已批准

- 根据用户批准，将故事状态从Draft更新为Approved
- 故事012.004文档已完成，可以开始实施

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

docs/stories/012.004.story.md

@@ -1,7 +1,7 @@
 # 故事 012.004：订单统计与数据统计API
 
 ## 状态
-Draft
+Approved
 
 ## 故事
 **作为**企业用户，