feat: add AI retouch before-after comparison

suixinkan/Features/TravelAlbum/Models/TravelAlbumModels.swift

@@ -403,23 +403,45 @@ enum TravelAlbumAIRetouchWorkflow: Sendable, Equatable {
     }
 }
 
-/// AI 修图模板，包含业务 ID、展示名称和预览图地址。
+/// AI 修图模板，包含业务 ID、展示名称、卡片预览图及前后对比图片地址。
 struct TravelAlbumAIRetouchTemplate: Decodable, Sendable, Equatable, Hashable, Identifiable {
     let id: Int
     let name: String
     let previewURL: String
+    let beforeURL: String
+    let afterURL: String
 
     enum CodingKeys: String, CodingKey {
         case id
         case name
         case previewURL = "preview_url"
+        case beforeURL = "before_url"
+        case afterURL = "after_url"
     }
 
     /// 创建 AI 修图模板。
-    init(id: Int, name: String, previewURL: String) {
+    init(
+        id: Int,
+        name: String,
+        previewURL: String,
+        beforeURL: String = "",
+        afterURL: String = ""
+    ) {
         self.id = id
         self.name = name
         self.previewURL = previewURL
+        self.beforeURL = beforeURL
+        self.afterURL = afterURL
+    }
+
+    /// 解码模板；前后对比字段缺失或为 null 时按空字符串兼容旧接口响应。
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        id = try container.decode(Int.self, forKey: .id)
+        name = try container.decode(String.self, forKey: .name)
+        previewURL = try container.decode(String.self, forKey: .previewURL)
+        beforeURL = (try? container.decodeIfPresent(String.self, forKey: .beforeURL)) ?? ""
+        afterURL = (try? container.decodeIfPresent(String.self, forKey: .afterURL)) ?? ""
     }
 }