Use compact [ ] select button and show active address above actions

Replace [select] with [ ] to avoid wrapping the full address line.
ACTIVE label stays as-is for discoverability. Show the currently
active address (full, untruncated, with color dot) above the Send
and Receive buttons on the home screen.

src/popup/index.html

@@ -178,6 +178,12 @@
                     class="text-2xl font-bold mb-2 min-h-[2rem]"
                 ></div>
 
+                <!-- active address display -->
+                <div
+                    id="active-address-display"
+                    class="text-xs break-all mb-3"
+                ></div>
+
                 <!-- quick actions for active address -->
                 <div class="flex gap-2 mb-3">
                     <button