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/Statistics/ViewModels/StatisticsViewModel.swift

@@ -6,21 +6,20 @@
 //
 
 import Foundation
-import Observation
+import Combine
 
 @MainActor
-@Observable
 /// 数据统计页面 ViewModel，管理时间段、汇总数据、每日明细和分页状态。
-final class StatisticsViewModel {
-    var selectedPeriod: StatisticsPeriod = .today
-    private(set) var loading = false
-    private(set) var loadingMore = false
-    private(set) var summary = StatisticsSummaryResponse()
-    private(set) var dailyItems: [StatisticsDailyItem] = []
-    private(set) var totalDailyCount = 0
-    private(set) var lastRefreshAt: Date?
+final class StatisticsViewModel: ObservableObject {
+    @Published var selectedPeriod: StatisticsPeriod = .today
+    @Published private(set) var loading = false
+    @Published private(set) var loadingMore = false
+    @Published private(set) var summary = StatisticsSummaryResponse()
+    @Published private(set) var dailyItems: [StatisticsDailyItem] = []
+    @Published private(set) var totalDailyCount = 0
+    @Published private(set) var lastRefreshAt: Date?
 
-    private var page = 1
+    @Published private var page = 1
     private let pageSize = 15
 
     /// 当前日数据是否还有下一页。