Show contract calls as "Approve USDT" instead of "0.0000 ETH"

Contract interactions (approve, swap, etc.) now display the method
name and token symbol instead of the meaningless 0 ETH value.
Blockscout provides the method name and whether the target is a
contract — parseTx uses these plus TOKEN_BY_ADDRESS to produce
labels like "Approve USDT" or "Swap LINK".

Added directionLabel field to parsed transactions so renderers
don't need to know about the sent/received/contract distinction.

Also: clicking a transaction on the home screen now opens the
transaction detail view instead of navigating to the address
detail view.

src/popup/views/transactionDetail.js

@@ -110,6 +110,7 @@ function show(tx) {
             isError: tx.isError,
             fromEns: tx.fromEns || null,
             toEns: tx.toEns || null,
+            directionLabel: tx.directionLabel || null,
         },
     };
     render();
@@ -121,7 +122,9 @@ function render() {
     $("tx-detail-hash").innerHTML = txHashHtml(tx.hash);
     $("tx-detail-from").innerHTML = txAddressHtml(tx.from, tx.fromEns);
     $("tx-detail-to").innerHTML = txAddressHtml(tx.to, tx.toEns);
-    $("tx-detail-value").textContent = tx.value + " " + tx.symbol;
+    $("tx-detail-value").textContent = tx.value
+        ? tx.value + " " + tx.symbol
+        : tx.directionLabel + " " + tx.symbol;
     $("tx-detail-time").textContent =
         isoDate(tx.timestamp) + " (" + timeAgo(tx.timestamp) + ")";
     $("tx-detail-status").textContent = tx.isError ? "Failed" : "Success";