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/Payment/ViewModels/PaymentViewModel.swift

@@ -20,8 +20,8 @@ final class PaymentCollectionViewModel: ObservableObject {
     @Published var remarkText = ""
     @Published var currentPayUrl = ""
     @Published var qrImage: UIImage?
-    @Published var isLoading = false
-    @Published var isPolling = false
+    private var isLoading = false
+    private var isPolling = false
     @Published var errorMessage: String?
     @Published var status: PaymentCollectionStatus = .idle
 
@@ -193,7 +193,7 @@ private extension String {
 /// 收款记录 ViewModel，管理收款记录加载、日期分组和汇总兜底。
 final class PaymentCollectionRecordViewModel: ObservableObject {
     @Published var groups: [PaymentCollectionRecordGroup] = []
-    @Published var isLoading = false
+    private var isLoading = false
     @Published var errorMessage: String?
 
     /// 加载当前景区收款记录，无景区时不请求接口。