fix: 修复 ResultView Live Photo 预览宽度铺满问题

PHLivePhotoView 无 intrinsic content size，SwiftUI 的
.aspectRatio() 对 UIViewRepresentable 无效。
改用 Color.clear + aspectRatio 撑出正确比例容器，
再用 .overlay 放入 Live Photo 预览。
同时移除 .frame(maxWidth: .infinity) 避免强制撑满。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

to-live-photo/to-live-photo/Views/ResultView.swift

@@ -83,13 +83,16 @@ struct ResultView: View {
                 let photoSize = livePhoto.size
                 let ratio = photoSize.width / max(photoSize.height, 1)
                 SoftCard(padding: DesignTokens.Spacing.md) {
-                    LivePhotoPreviewView(livePhoto: livePhoto)
+                    // PHLivePhotoView 无 intrinsic size，用 Color.clear 撑出正确比例
+                    Color.clear
                         .aspectRatio(ratio, contentMode: .fit)
                         .frame(maxHeight: 360)
+                        .overlay {
+                            LivePhotoPreviewView(livePhoto: livePhoto)
+                        }
                         .clipShape(RoundedRectangle(cornerRadius: DesignTokens.Radius.lg))
                         .accessibilityLabel(String(localized: "result.livePhotoPreview.accessibilityLabel"))
                 }
-                .frame(maxWidth: .infinity)
             }
 
             Text(String(localized: "result.livePhotoPreview.hint"))