feat(ui): add ShareSheet component for multi-channel post sharing

Add ShareSheet component that provides native sharing options (WeChat, Moments, copy link, etc.) replacing the previous clipboard-only approach. Also change like icon from heart to thumb-up to better match the share functionality.

src/components/business/index.ts

@@ -23,3 +23,4 @@ export { default as VoteCard } from './VoteCard';
 export { default as VoteEditor } from './VoteEditor';
 export { default as VotePreview } from './VotePreview';
 export { default as ReportDialog } from './ReportDialog';
+export { default as ShareSheet } from './ShareSheet';