fix: the recipient warning says what it checked and skips addresses that have received ETH (closes #528)

The transaction count the node reports is what an address has sent, so
an address that only receives, such as a savings address, got the "ZERO
transaction history" box on every send. The check now also asks the node
for the recipient's balance and warns only when both are zero. The box
says the address has never sent a transaction and holds no ETH, naming
the active network's native token as the contract warning does.

Model: opus-5-5

src/popup/index.html

@@ -634,17 +634,12 @@
                     </div>
                 </div>
                 <div id="confirm-warnings" class="mb-2 invisible"></div>
-                <div id="confirm-recipient-warning" class="mb-2 invisible">
-                    <div
-                        class="border border-red-500 border-dashed p-2 text-xs font-bold text-red-500"
-                    >
-                        WARNING: The recipient address has ZERO transaction
-                        history. This may indicate a fresh or unused address.
-                        Double-check the address before sending.
-                    </div>
-                </div>
-                <!-- Its sentence names the network's native token, so show()
-                in confirmTx.js sets it. -->
+                <!-- These two sentences name the network's native token, so
+                show() in confirmTx.js sets them. -->
+                <div
+                    id="confirm-recipient-warning"
+                    class="mb-2 border border-red-500 border-dashed p-2 text-xs font-bold text-red-500 invisible"
+                ></div>
                 <div
                     id="confirm-contract-warning"
                     class="mb-2 border border-red-500 border-dashed p-2 text-xs font-bold text-red-500 invisible"