refactor(coach): 重构教练组件，统一导入并简化UI实现与类型定义

components/coach/index.ts

@@ -0,0 +1,11 @@
+// Coach 组件导出
+export { default as ChatComposer } from './ChatComposer';
+export { default as ChatMessage } from './ChatMessage';
+export { default as DietInputCard } from './DietInputCard';
+export { default as DietOptionsCard } from './DietOptionsCard';
+export { default as DietPlanCard } from './DietPlanCard';
+export { default as QuickChips } from './QuickChips';
+export { default as WeightInputCard } from './WeightInputCard';
+
+// 类型导出
+export * from './types';