Add address color dots and cached ENS reverse lookups

Deterministic colored dots derived from address bytes (16-color palette)
displayed before every address. ENS reverse resolution for transaction
counterparties with 12-hour localStorage cache.

src/popup/index.html

@@ -196,11 +196,15 @@
                     <h2 class="font-bold" id="address-title">Address</h2>
                 </div>
 
-                <div id="address-ens" class="font-bold mb-1 hidden"></div>
                 <div
-                    class="flex text-xs mb-3 cursor-pointer"
+                    id="address-ens"
+                    class="font-bold mb-1 hidden flex items-center"
+                ></div>
+                <div
+                    class="flex text-xs mb-3 cursor-pointer items-center"
                     title="Click to copy"
                 >
+                    <span id="address-dot"></span>
                     <span
                         id="address-full"
                         style="width: 42ch; max-width: 100%"