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/shared/transactions.js

@@ -139,9 +139,18 @@ async function fetchRecentTransactions(address, blockscoutUrl, count = 25) {
 
     // When a token transfer shares a hash with a normal tx, the normal tx
     // is the contract call (0 ETH) and the token transfer has the real
-    // amount and symbol. Replace the normal tx with the token transfer.
+    // amount and symbol. Replace the normal tx with the token transfer,
+    // but preserve contract call metadata (direction, label, method) so
+    // swaps and other contract interactions display correctly.
     for (const tt of ttJson.items || []) {
         const parsed = parseTokenTransfer(tt, addrLower);
+        const existing = txsByHash.get(parsed.hash);
+        if (existing && existing.direction === "contract") {
+            parsed.direction = "contract";
+            parsed.directionLabel = existing.directionLabel;
+            parsed.isContractCall = true;
+            parsed.method = existing.method;
+        }
         txsByHash.set(parsed.hash, parsed);
     }