Bitcoin to sBTC swap transaction not appearing in mempool + missing fee selection

## Description User performed a Bitcoin to sBTC swap through Leather wallet, but the resulting Bitcoin transaction is not appearing in the mempool. Additionally, the user was not prompted to select a transaction fee rate during the swap process. ## Steps to Reproduce 1. Initiate Bitcoin to sBTC swap in Leather wallet 2. Complete the swap transaction 3. Check transaction status in Leather's activity tab 4. Navigate to the mempool link provided by Leather ## Expected Behavior - Transaction should appear in the mempool after being broadcast - User should be prompted to select an appropriate fee rate for the Bitcoin transaction - Activity tab should show accurate transaction status ## Actual Behavior - Mempool shows "Transaction not found. Waiting for it to appear in the mempool..." - No fee rate selection was presented to the user during the swap process - Transaction appears to have been created but not successfully broadcast to the Bitcoin network ## Transaction Details - **Mempool Link**: https://mempool.space/tx/ebbca2da6e48d6a44df51fcfb4ab3ed111d31be7ab9b970e81826f375a61ab32 - **Transaction ID**: `ebbca2da6e48d6a44df51fcfb4ab3ed111d31be7ab9b970e81826f375a61ab32` - **Status**: Not found in mempool - **Swap Type**: Bitcoin → sBTC ## Questions 1. **Is this expected behavior?** Should Bitcoin to sBTC swaps result in transactions that don't immediately appear in the mempool? 2. **Fee Selection**: How does Leather determine the fee rate for Bitcoin transactions when no user selection is prompted? Is this automatic fee selection intended behavior? 3. **Transaction Broadcasting**: Are there specific conditions under which Bitcoin transactions might not be broadcast to the network immediately? ## Additional Context - User has provided a screenshot (attached) - This appears to be related to the sBTC bridge functionality - Issue may be related to transaction broadcasting or fee estimation logic ## Possible Investigation Areas - [ ] Transaction broadcasting mechanism for sBTC swaps - [ ] Fee estimation and selection UI/UX - [ ] Mempool integration and status checking - [ ] sBTC bridge transaction flow - [ ] Error handling for failed broadcasts ## Priority **Medium** - Affects core wallet functionality and user experience, but user funds appear to be safe (transaction exists, just not broadcast) <img width="1436" height="444" alt="Image" src="https://github.com/user-attachments/assets/1c171db3-f2a6-4baf-9f1f-c625b9612f42" /> <img width="398" height="214" alt="Image" src="https://github.com/user-attachments/assets/d85880b6-69ff-4c7d-a75e-fbcf0ff852c2" />