从 iOS 17 Observation 迁移至 iOS 16 兼容的 Combine 架构

将最低部署版本降至 iOS 16，以 ObservableObject 替换 @Observable，新增导航与 UI 兼容层，并补充登录冒烟 UI 测试。

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

suixinkan/Core/Design/AppContentUnavailableView.swift

@@ -0,0 +1,75 @@
+//
+//  AppContentUnavailableView.swift
+//  suixinkan
+//
+//  Created by Codex on 2026/6/26.
+//
+
+import SwiftUI
+
+/// iOS 16 兼容的空状态视图；iOS 17+ 自动使用系统 AppContentUnavailableView。
+struct AppContentUnavailableView<LabelContent: View, DescriptionContent: View, ActionsContent: View>: View {
+    private let label: LabelContent
+    private let description: DescriptionContent
+    private let actions: ActionsContent
+
+    init(
+        @ViewBuilder label: () -> LabelContent,
+        @ViewBuilder description: () -> DescriptionContent,
+        @ViewBuilder actions: () -> ActionsContent
+    ) {
+        self.label = label()
+        self.description = description()
+        self.actions = actions()
+    }
+
+    var body: some View {
+        if #available(iOS 17.0, *) {
+            AppContentUnavailableView {
+                label
+            } description: {
+                description
+            } actions: {
+                actions
+            }
+        } else {
+            VStack(spacing: AppMetrics.Spacing.small) {
+                label
+                    .font(.system(size: AppMetrics.FontSize.title3, weight: .semibold))
+                    .foregroundStyle(AppDesign.textPrimary)
+                description
+                    .font(.system(size: AppMetrics.FontSize.subheadline))
+                    .foregroundStyle(AppDesign.textSecondary)
+                    .multilineTextAlignment(.center)
+                actions
+                    .padding(.top, AppMetrics.Spacing.xSmall)
+            }
+            .frame(maxWidth: .infinity)
+            .padding(AppMetrics.Spacing.large)
+        }
+    }
+}
+
+extension AppContentUnavailableView where LabelContent == Label<Text, Image>, DescriptionContent == EmptyView, ActionsContent == EmptyView {
+    init(_ title: String, systemImage: String) {
+        self.init {
+            Label(title, systemImage: systemImage)
+        } description: {
+            EmptyView()
+        } actions: {
+            EmptyView()
+        }
+    }
+}
+
+extension AppContentUnavailableView where LabelContent == Label<Text, Image>, DescriptionContent == Text, ActionsContent == EmptyView {
+    init(_ title: String, systemImage: String, description: Text) {
+        self.init {
+            Label(title, systemImage: systemImage)
+        } description: {
+            description
+        } actions: {
+            EmptyView()
+        }
+    }
+}

suixinkan/Core/Design/GlobalLoadingCenter.swift

@@ -77,7 +77,7 @@ final class GlobalLoadingCenter {
 fileprivate final class GlobalLoadingState: ObservableObject {
     @Published fileprivate var isVisible = false
     @Published fileprivate var message = ""
-    fileprivate var activeCount = 0
+    @Published fileprivate var activeCount = 0
 }
 
 /// Lottie Loading 动画容器，负责播放主包中的 loading.json。