修复确认按钮正常模式下不可见的问题

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

LearnEnglish/LearnEnglish/Views/SpellingInputView.swift

@@ -71,7 +71,7 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
         let bgImage = renderer.image { ctx in
             let gradient = CGGradient(
                 colorsSpace: CGColorSpaceCreateDeviceRGB(),
-                colors: [UIColor(white: 1, alpha: 0.65).cgColor, UIColor(white: 1, alpha: 0.2).cgColor] as CFArray,
+                colors: [UIColor(red: 0.6, green: 0.75, blue: 0.95, alpha: 0.7).cgColor, UIColor(red: 0.3, green: 0.55, blue: 0.85, alpha: 0.45).cgColor] as CFArray,
                 locations: [0, 0.5]
             )!
             ctx.cgContext.drawLinearGradient(gradient,
@@ -79,15 +79,9 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
         }
         glassButton.setBackgroundImage(bgImage, for: .normal)
 
-        var titleConfig = UIButton.Configuration.plain()
-        titleConfig.title = "确认"
-        titleConfig.baseForegroundColor = .white
-        titleConfig.titleTextAttributesTransformer = UIConfigurationTextAttributesTransformer { incoming in
-            var outgoing = incoming
-            outgoing.font = .systemFont(ofSize: 16, weight: .semibold)
-            return outgoing
-        }
-        glassButton.configuration = titleConfig
+        glassButton.setTitle("确认", for: .normal)
+        glassButton.setTitleColor(.white, for: .normal)
+        glassButton.titleLabel?.font = .systemFont(ofSize: 16, weight: .semibold)
         glassButton.addAction(UIAction { [weak self] _ in
             self?.onSubmit?()
         }, for: .touchUpInside)