feat: add iOS support and harden receipt scanning

app/ios/ScanReceipts/Features/Auth/AuthFlowView.swift

@@ -0,0 +1,34 @@
+import SwiftUI
+
+/// Shown for `AppState.phase == .signedOut` (see `App/RootView.swift`, which
+/// depends on this exact type name and its zero-argument initializer). Owns
+/// simple in-feature navigation between "Anmelden", "Registrieren", and the
+/// post-signup "bitte bestätige deine E-Mail" screen — none of that belongs
+/// in `AppState` since none of it affects whether the user is actually
+/// signed in; `AppState.phase` only changes once a real session exists.
+struct AuthFlowView: View {
+    private enum Screen: Equatable {
+        case login
+        case signup
+        case verificationPending(email: String)
+    }
+
+    @State private var screen: Screen = .login
+
+    var body: some View {
+        Group {
+            switch screen {
+            case .login:
+                LoginView(onSwitchToSignup: { screen = .signup })
+            case .signup:
+                SignupView(
+                    onSignupSucceeded: { email in screen = .verificationPending(email: email) },
+                    onSwitchToLogin: { screen = .login }
+                )
+            case .verificationPending(let email):
+                VerificationPendingView(email: email, onGoToLogin: { screen = .login })
+            }
+        }
+        .animation(.default, value: screen)
+    }
+}