Introduce unified design tokens and migrate Home, Orders, and Statistics UI.

Establish AppColor/AppFont/AppSpacing/AppRadius theming, shared components, and design-system docs so pilot screens align with Android while keeping iOS-native spacing and touch targets.

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

suixinkan/Theme/AppFont.swift

@@ -0,0 +1,54 @@
+//
+//  AppFont.swift
+//  suixinkan
+//
+
+import UIKit
+
+/// 应用字体层级，基于 8pt 网格与 SF Pro（System）。
+enum AppFont {
+
+    case caption
+    case captionMedium
+    case body
+    case bodyMedium
+    case subtitle
+    case title
+    case metric
+    case display
+
+    /// 对应 UIFont。
+    var uiFont: UIFont {
+        switch self {
+        case .caption:
+            return .systemFont(ofSize: 12, weight: .regular)
+        case .captionMedium:
+            return .systemFont(ofSize: 12, weight: .medium)
+        case .body:
+            return .systemFont(ofSize: 14, weight: .regular)
+        case .bodyMedium:
+            return .systemFont(ofSize: 14, weight: .medium)
+        case .subtitle:
+            return .systemFont(ofSize: 16, weight: .medium)
+        case .title:
+            return .systemFont(ofSize: 16, weight: .bold)
+        case .metric:
+            return .systemFont(ofSize: 18, weight: .bold)
+        case .display:
+            return .systemFont(ofSize: 28, weight: .semibold)
+        }
+    }
+
+    /// 将字体应用到 UILabel。
+    func apply(to label: UILabel) {
+        label.font = uiFont
+    }
+}
+
+extension UIFont {
+
+    /// 通过 `AppFont` 获取系统字体。
+    static func app(_ style: AppFont) -> UIFont {
+        style.uiFont
+    }
+}