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/addressDetail.js

@@ -186,8 +186,10 @@ function renderTransactions(txs) {
     for (const tx of txs) {
         const counterparty = tx.direction === "sent" ? tx.to : tx.from;
         const ensName = ensNameMap.get(counterparty) || null;
-        const dirLabel = tx.direction === "sent" ? "Sent" : "Received";
-        const amountStr = escapeHtml(tx.value + " " + tx.symbol);
+        const dirLabel = tx.directionLabel;
+        const amountStr = tx.value
+            ? escapeHtml(tx.value + " " + tx.symbol)
+            : escapeHtml(tx.symbol);
         const maxAddr = Math.max(10, 36 - Math.max(0, amountStr.length - 10));
         const displayAddr = ensName || truncateMiddle(counterparty, maxAddr);
         const addrStr = escapeHtml(displayAddr);