feat: 添加举报功能前端支持

- 新增 reportService API 服务
- 新增 ReportDialog 举报对话框组件
- 集成举报入口到 PostCard、CommentItem、LongPressMenu

Made-with: Cursor

src/components/business/index.ts

@@ -22,3 +22,4 @@ export { default as TabBar } from './TabBar';
 export { default as VoteCard } from './VoteCard';
 export { default as VoteEditor } from './VoteEditor';
 export { default as VotePreview } from './VotePreview';
+export { default as ReportDialog } from './ReportDialog';