fix: say a contract creation has no recipient instead of a blank line (closes #250)

A transaction with no `to` showed a blank recipient line on the wait,
success and error screens and the transaction detail view: an empty
address, with a colour dot whose colour was `undefined`. The approval
screen showed "(contract creation)".

All five now say "This transaction creates a new contract. It has no
recipient." A transaction with a real `to` is unchanged. The new test
drives each screen both ways.

Model: opus-5-5

src/popup/views/approval.js

@@ -1,6 +1,7 @@
 const {
     $,
     addressTitle,
+    CONTRACT_CREATION_TEXT,
     escapeHtml,
     showView,
     showError,
@@ -320,7 +321,7 @@ function showTxApproval(details) {
         toHtml += approvalAddressHtml(toAddr);
         $("approve-tx-to").innerHTML = toHtml;
     } else {
-        $("approve-tx-to").innerHTML = escapeHtml("(contract creation)");
+        $("approve-tx-to").innerHTML = escapeHtml(CONTRACT_CREATION_TEXT);
     }
 
     const ethValueFormatted = formatTxValue(