feat: Optimize capsule color computation by using Style.qml property

Commons/Style.qml

@@ -104,4 +104,7 @@ Singleton {
       return Math.round(barHeight * 0.82);
     }
   }
+  readonly property color capsuleColor: Settings.data.bar.showCapsule ?
+    Qt.alpha(Color.mSurfaceVariant, Settings.data.bar.capsuleOpacity) :
+    Color.transparent
 }