feat: add frontend development guidelines and structure documentation

- Introduced API guidelines for interface contracts and request handling.
- Added design tokens usage guidelines for consistent styling across the project.
- Established DTO guidelines for defining request parameters and response data types.
- Created frontend structure guidelines to clarify directory organization and code placement rules.
- Compiled a comprehensive frontend development guideline document covering various aspects of the development process.
- Implemented quality guidelines to ensure code maintainability and adherence to best practices.

AGENTS.md.md

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+- 把 ~/vault 当作你长期的工作记忆区。
+- 尽量把笔记整理得有条理，别搞得到处都是碎片记录。
+- 准确地把待办事项、人员、项目、每日总结和草稿分类放好。
+- 把做过的决定、遇到的卡点、负责人、日期和有用的链接好好保存下来。
+- 如果没有什么实质性的新进展，不要随意修改知识库里的文件。