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/UI/RemoteImage.swift

@@ -40,7 +40,7 @@ struct RemoteImage<Placeholder: View>: View {
                 placeholder()
             }
         }
-        .onChange(of: normalizedURLString) { _, _ in
+        .onChange(of: normalizedURLString) { _ in
             didFail = false
         }
     }