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/AppShadow.swift

@@ -0,0 +1,18 @@
+//
+//  AppShadow.swift
+//  suixinkan
+//
+
+import UIKit
+
+/// 轻量阴影，仅用于登录表单等浮层卡片。
+enum AppShadow {
+
+    /// 为 layer 应用标准卡片阴影（登录表单等）。
+    static func applyCardShadow(to layer: CALayer) {
+        layer.shadowColor = UIColor.black.cgColor
+        layer.shadowOpacity = 0.08
+        layer.shadowOffset = CGSize(width: 0, height: 4)
+        layer.shadowRadius = 12
+    }
+}