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 Coding/patterns/index.md

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+# Patterns
+
+保存至少经过两个独立项目或场景验证的跨项目模式。
+
+Pattern 应说明：
+
+- 触发条件
+- 核心机制
+- 适用与不适用边界
+- 支撑它的 learning
+- 已提升到哪些执行资产