resolve alpha button override issues in configuration

ios/MullvadVPN/Extensions/UIImage+Helpers.swift

@@ -26,4 +26,10 @@ extension UIImage {
 
         return resizedImage.withRenderingMode(renderingMode)
     }
+
+    func withAlpha(_ alpha: CGFloat) -> UIImage? {
+        return UIGraphicsImageRenderer(size: size, format: imageRendererFormat).image { _ in
+            draw(in: CGRect(origin: .zero, size: size), blendMode: .normal, alpha: alpha)
+        }
+    }
 }

ios/MullvadVPN/Views/AppButton.swift

@@ -119,16 +119,23 @@ class AppButton: CustomButton {
                 return updatedAttributeContainer
             }
 
-        let configurationHandler: UIButton.ConfigurationUpdateHandler = { button in
-            button.alpha = !button.isEnabled ? 0.5 : 1.0
+        let configurationHandler: UIButton.ConfigurationUpdateHandler = { [weak self] button in
+            guard let self else { return }
             button.configuration?.baseForegroundColor = button.state.customButtonTitleColor
+            updateButtonBackground()
         }
         configuration = config
         configurationUpdateHandler = configurationHandler
     }
 
     /// Set background image based on current style.
     private func updateButtonBackground() {
-        configuration?.background.image = style.backgroundImage
+        if isEnabled {
+            // Load the normal image and set it as the background
+            configuration?.background.image = style.backgroundImage
+        } else {
+            // Adjust the image for the disabled state
+            configuration?.background.image = style.backgroundImage.withAlpha(0.5)
+        }
     }
 }

ios/MullvadVPN/Views/CustomButton.swift

@@ -14,7 +14,7 @@ extension UIControl.State {
         case .normal:
             return UIColor.AppButton.normalTitleColor
         case .disabled:
-            return UIColor.AppButton.disabledTitleColor
+            return UIColor.AppButton.disabledTitleColor.withAlphaComponent(0.5)
         case .highlighted:
             return UIColor.AppButton.highlightedTitleColor
         default: