feat: add iOS support and harden receipt scanning

app/ios/ScanReceipts/Design/ZenithSpacing.swift

@@ -0,0 +1,24 @@
+import CoreGraphics
+
+/// The web app's 4px-base spacing scale (`DESIGN (1).md` → Layout & Spacing:
+/// `spacing.unit: 4px`, `stack-sm/md/lg/xl`, `margin-mobile`). Use these
+/// instead of ad-hoc padding numbers so spacing stays consistent with the
+/// web app's rhythm.
+enum ZenithSpacing {
+    /// The 4px base unit itself — for the rare one-off that doesn't fit a
+    /// named step below.
+    static let unit: CGFloat = 4
+
+    static let xs: CGFloat = 8   // stack-sm
+    static let sm: CGFloat = 16  // margin-mobile
+    static let md: CGFloat = 24  // stack-md / card internal padding
+    static let lg: CGFloat = 48  // stack-lg
+    static let xl: CGFloat = 80  // stack-xl
+
+    /// Card internal padding — `DESIGN (1).md` → Components → Cards:
+    /// "Content within cards should follow the 24px internal padding rule."
+    static let cardPadding: CGFloat = md
+    /// Screen-edge margin on a phone-width layout (mobile margin, not the
+    /// 64px desktop margin, which doesn't apply on iPhone).
+    static let screenMargin: CGFloat = sm
+}