移除 MJRefresh 依赖，恢复 SwiftUI 系统下拉刷新。

同时收紧各 ViewModel 内部 isLoading 可见性，避免不必要的视图刷新。

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

suixinkan/Features/PunchPoint/ViewModels/PunchPointViewModels.swift

@@ -15,7 +15,7 @@ final class PunchPointListViewModel: ObservableObject {
     @Published var items: [PunchPointItem] = []
     @Published var selectedDetail: PunchPointItem?
     @Published var errorMessage: String?
-    @Published var isLoading = false
+    private var isLoading = false
     @Published var isLoadingMore = false
     @Published var total = 0