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/ReportDialog/index.ts

@@ -0,0 +1,2 @@
+export { ReportDialog } from './ReportDialog';
+export type { ReportDialogProps } from './ReportDialog';