feat: 视频列表增加 checkbox 选择列和全选按钮，修复 PlayInfo 解码失败导致下载面板无选项的问题

- PlayInfo 添加 CodingKeys 映射 PascalCase JSON 字段（PlayURL/Definition/Duration/Size/Format）\n- Table 第一列增加圆形 checkbox 图标，点击可切换选中状态\n- 增加全选/取消全选按钮\n- prepareDownload 增加错误提示\n- 下载面板无播放地址时显示提示文字

apps/macos/VODManager/Sources/VODManager/Models/Models.swift

@@ -131,6 +131,14 @@ struct PlayInfo: Codable, Equatable {
     var duration: String?
     var size: Int64?
     var format: String?
+
+    enum CodingKeys: String, CodingKey {
+        case playURL = "PlayURL"
+        case definition = "Definition"
+        case duration = "Duration"
+        case size = "Size"
+        case format = "Format"
+    }
 }
 
 struct CategoryItem: Identifiable, Codable, Equatable {

apps/macos/VODManager/Sources/VODManager/Views/DownloadPanelView.swift

@@ -37,15 +37,20 @@ struct DownloadPanelView: View {
                         Text(item.video.title)
                             .lineLimit(1)
                         Spacer()
-                        Picker("清晰度", selection: Binding(
-                            get: { selectedDefinitions[item.video.videoId] ?? item.playInfos.first?.definition ?? "" },
-                            set: { selectedDefinitions[item.video.videoId] = $0 }
-                        )) {
-                            ForEach(item.playInfos, id: \.definition) { info in
-                                Text("\(info.definition) - \(formatSize(info.size))").tag(info.definition)
+                        if item.playInfos.isEmpty {
+                            Text("无可用播放地址")
+                                .foregroundStyle(.secondary)
+                        } else {
+                            Picker("清晰度", selection: Binding(
+                                get: { selectedDefinitions[item.video.videoId] ?? item.playInfos.first?.definition ?? "" },
+                                set: { selectedDefinitions[item.video.videoId] = $0 }
+                            )) {
+                                ForEach(item.playInfos, id: \.definition) { info in
+                                    Text("\(info.definition) - \(formatSize(info.size))").tag(info.definition)
+                                }
                             }
+                            .frame(width: 200)
                         }
-                        .frame(width: 200)
                     }
                 }
             }

apps/macos/VODManager/Sources/VODManager/Views/VideoListView.swift

@@ -38,6 +38,14 @@ struct VideoListView: View {
                 }
                 .disabled(selectedVideos.isEmpty || isLoading)
 
+                Button("全选") {
+                    if selectedVideos.count == videos.count {
+                        selectedVideos.removeAll()
+                    } else {
+                        selectedVideos = Set(videos.map(\.videoId))
+                    }
+                }
+
                 Button("批量删除") {
                     Task { await batchDelete() }
                 }
@@ -65,6 +73,19 @@ struct VideoListView: View {
             }
 
             Table(of: VideoItem.self, selection: $selectedVideos) {
+                TableColumn("") { video in
+                    Image(systemName: selectedVideos.contains(video.videoId) ? "checkmark.circle.fill" : "circle")
+                        .foregroundStyle(selectedVideos.contains(video.videoId) ? .blue : .secondary)
+                        .onTapGesture {
+                            if selectedVideos.contains(video.videoId) {
+                                selectedVideos.remove(video.videoId)
+                            } else {
+                                selectedVideos.insert(video.videoId)
+                            }
+                        }
+                }
+                .width(min: 30, ideal: 30, max: 30)
+
                 TableColumn("标题") { video in
                     HStack {
                         AsyncImage(url: video.coverURL.flatMap(URL.init)) { image in
@@ -172,15 +193,24 @@ struct VideoListView: View {
 
     private func prepareDownload() async {
         isLoading = true
+        errorMessage = nil
         var results: [(video: VideoItem, playInfos: [PlayInfo])] = []
+        var errors: [String] = []
         for video in videos where selectedVideos.contains(video.videoId) {
             do {
                 let response = try await VODClient.shared.getPlayInfo(videoId: video.videoId)
                 results.append((video, response.playInfos))
+                if response.playInfos.isEmpty {
+                    errors.append("「\(video.title)」无可用播放地址")
+                }
             } catch {
                 results.append((video, []))
+                errors.append("「\(video.title)」获取播放信息失败：\(error.localizedDescription)")
             }
         }
+        if !errors.isEmpty {
+            errorMessage = errors.joined(separator: "\n")
+        }
         downloadResults = results
         showDownloadPanel = true
         isLoading = false