Migrate from iOS 17 Observation to iOS 16-compatible Combine architecture.

Lower deployment target to iOS 16, replace @Observable with ObservableObject, add navigation and UI compatibility shims, and include login smoke UI tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan/Features/Tasks/Views/TaskSelectionViews.swift

@@ -57,13 +57,13 @@ struct TaskOrderSelectionView: View {
 
 /// 任务云盘文件选择页面，供发布任务时选择云盘附件。
 struct TaskCloudFileSelectionView: View {
-    @Environment(TaskAPI.self) private var taskAPI
-    @Environment(ToastCenter.self) private var toastCenter
+    @Environment(\.taskAPI) private var taskAPI
+    @EnvironmentObject private var toastCenter: ToastCenter
     @Environment(\.dismiss) private var dismiss
 
     let onConfirm: ([TaskCloudSelectionItem]) -> Void
 
-    @State private var viewModel = TaskCloudFileSelectionViewModel()
+    @StateObject private var viewModel = TaskCloudFileSelectionViewModel()
 
     var body: some View {
         VStack(spacing: 0) {
@@ -108,7 +108,7 @@ struct TaskCloudFileSelectionView: View {
                 }
             }
             .pickerStyle(.segmented)
-            .onChange(of: viewModel.selectedFilter) { _, _ in
+            .onChange(of: viewModel.selectedFilter) { _ in
                 Task { await reload() }
             }
         }