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.

AI-RD-Workflow/40-workflows/rd-workflow.md

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+---
+id: RD-WORKFLOW-AI-RD
+type: workflow
+status: draft
+created: 2026-06-29
+---
+
+# RD 工作流
+
+1. 接收 SE 侧 OR、DR。
+2. 使用 `rd-design-generate` 生成 DS。
+3. 将 DS 拆为 TASK。
+4. 明确每个 TASK 的输入、输出、文件范围、测试点。
+5. 使用 AI agent 或人工编码。
+6. 将代码变更关联回 TASK/DS。
+7. 进入 Gate 3 和 Gate 4。