[2026-07-resubmission] Add guest browsing flow with App Attest session for App Review resubmission

Adds a pre-login public store locator (guest session via DeviceCheck/App
Attest, keychain-backed token storage) so the app no longer forces sign-in
before showing any content, plus updated support URL metadata.

Sources/PediFoods/Views/Main/CartView.swift

@@ -4,6 +4,7 @@ import SwiftUI
 struct CartView: View {
     @Binding var appState: AppState
     @Binding var selectedTab: MainTab
+    @Binding var root: RootFlow
     @State var openCheckout = false
     @State var couponCode = ""
     @State var appliedCouponCode: String? = nil
@@ -148,6 +149,10 @@ struct CartView: View {
             summaryRow(title: "Total", value: formatCurrency(totalValue), highlighted: true)
 
             Button {
+                guard appState.session.isAuthenticated else {
+                    root = .auth
+                    return
+                }
                 openCheckout = true
             } label: {
                 HStack(spacing: 10) {