feat: add public tip claiming UI

- Extract fragment key from URL
- Check confirmations before allowing claim
- Add claim button with loading/error states
- Update SmirkAPI types for claimPublicTip

src/lib/api.ts

@@ -154,6 +154,8 @@ export interface PublicTipInfo {
   status: string;
   created_at: string;
   is_public: boolean;
+  funding_confirmations: number;
+  confirmations_required: number;
 }
 
 export async function getPublicTipInfo(tipId: string): Promise<PublicTipInfo> {