fix: display swaps and contract calls correctly in tx history (closes #3)

- Preserve contract call metadata (direction, label, method) when token
  transfers merge with normal txs in fetchRecentTransactions
- Handle 'contract' direction in counterparty display for home and
  address detail list views
- Add decoded calldata display to transaction detail view, fetching
  raw input from Blockscout and using decodeCalldata from approval.js
- Show 'Unknown contract call' with raw hex for unrecognized calldata
- Export decodeCalldata from approval.js for reuse

src/popup/views/approval.js

@@ -453,4 +453,4 @@ function init(ctx) {
     });
 }
 
-module.exports = { init, show };
+module.exports = { init, show, decodeCalldata };