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/Location/ForegroundLocationProvider.swift

@@ -7,7 +7,7 @@
 
 import CoreLocation
 import Foundation
-import Observation
+import Combine
 
 /// 前台定位结果实体，表示一次即时定位得到的坐标和可展示地址。
 struct ForegroundLocationResult: Equatable {
@@ -18,11 +18,10 @@ struct ForegroundLocationResult: Equatable {
 
 /// 前台定位 Provider，只负责当前页面主动请求位置，不缓存、不后台持续定位。
 @MainActor
-@Observable
-final class ForegroundLocationProvider: NSObject {
-    @ObservationIgnored private let manager = CLLocationManager()
-    @ObservationIgnored private let geocoder = CLGeocoder()
-    @ObservationIgnored private var continuation: CheckedContinuation<ForegroundLocationResult, Error>?
+final class ForegroundLocationProvider: NSObject, ObservableObject {
+    private let manager = CLLocationManager()
+    private let geocoder = CLGeocoder()
+    @Published private var continuation: CheckedContinuation<ForegroundLocationResult, Error>?
 
     override init() {
         super.init()