feat: Blink WiFi/Bluetooth icons while connecting (#2448)

Pulses the WiFi and Bluetooth status icons while a connection is in
progress (lock screen, DankBar control center button, control center
compound pill). The pulse is implemented as a reusable Widgets/DankBlink
component, and the wifi-connecting condition is centralized as
NetworkService.isWifiConnecting.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

quickshell/Services/LegacyNetworkService.qml

@@ -99,6 +99,9 @@ Singleton {
     }
 
     readonly property string wifiSignalIcon: {
+        if (isConnecting) {
+            return "wifi";
+        }
         if (!wifiConnected || networkStatus !== "wifi") {
             return "wifi_off";
         }