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/index.html

@@ -945,6 +945,15 @@
                     <div class="text-xs text-muted mb-1">To</div>
                     <div id="tx-detail-to" class="text-xs break-all"></div>
                 </div>
+                <div id="tx-detail-calldata-section" class="mb-4 hidden">
+                    <div class="text-xs text-muted mb-1">
+                        Contract interaction
+                    </div>
+                    <div
+                        id="tx-detail-calldata"
+                        class="text-xs break-all border border-border border-dashed p-2"
+                    ></div>
+                </div>
                 <div class="mb-4">
                     <div class="text-xs text-muted mb-1">Transaction hash</div>
                     <div id="tx-detail-hash" class="text-xs break-all"></div>