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/AppSpacing.swift

@@ -0,0 +1,33 @@
+//
+//  AppSpacing.swift
+//  suixinkan
+//
+
+import CoreGraphics
+
+/// 应用间距常量，基于 8pt 网格。
+enum AppSpacing {
+
+    static let xxs: CGFloat = 4
+    static let xs: CGFloat = 8
+    static let sm: CGFloat = 12
+    static let md: CGFloat = 16
+    static let lg: CGFloat = 24
+    static let xl: CGFloat = 32
+    static let xxl: CGFloat = 48
+
+    /// 屏幕水平内边距。
+    static let screenHorizontalInset: CGFloat = md
+
+    /// 最小可点击区域（Apple HIG）。
+    static let minTouchTarget: CGFloat = 44
+
+    /// 首页自定义 Header 高度。
+    static let homeHeaderHeight: CGFloat = 52
+
+    /// 主按钮默认高度。
+    static let buttonHeight: CGFloat = 46
+
+    /// 表单行默认高度。
+    static let formRowHeight: CGFloat = 52
+}