feat: add iOS support and harden receipt scanning

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

@@ -0,0 +1,86 @@
+import SwiftUI
+import AuthenticationServices
+import Foundation // PersonNameComponentsFormatter
+
+/// "Mit Apple anmelden" — placed below the email/password form on
+/// `LoginView`. Wired to the real backend: `POST /api/auth/apple`
+/// (`src/app/api/auth/apple/route.ts`) verifies the identity token Apple
+/// hands back and returns a session exactly like `/api/auth/login` does —
+/// see `AuthAPI.appleSignIn` / `AppState.signInWithApple`.
+struct AppleSignInButton: View {
+    @Environment(\.colorScheme) private var colorScheme
+    @EnvironmentObject private var appState: AppState
+
+    @State private var isSigningIn = false
+    /// Local, Apple-specific failures (token decode, user cancelled) — kept
+    /// separate from `appState.lastError` so a cancelled Apple sheet doesn't
+    /// show a stale email/password error underneath it, or vice versa.
+    @State private var localErrorMessage: String?
+
+    var body: some View {
+        VStack(spacing: ZenithSpacing.unit * 2) {
+            SignInWithAppleButton(.signIn) { request in
+                request.requestedScopes = [.fullName, .email]
+            } onCompletion: { result in
+                handle(result)
+            }
+            // Apple's Human Interface Guidelines fix this button's own shape
+            // and colors — not overridable to match Zenith Silver's 0px
+            // corners, and Apple explicitly does not allow restyling it.
+            .signInWithAppleButtonStyle(colorScheme == .dark ? .white : .black)
+            .frame(maxWidth: .infinity, minHeight: 50)
+            .clipShape(RoundedRectangle(cornerRadius: 8, style: .continuous))
+            .disabled(isSigningIn)
+            .overlay {
+                if isSigningIn {
+                    ProgressView().tint(.white)
+                }
+            }
+
+            // A backend-side failure (invalid token, server error, ...) sets
+            // `appState.lastError`, which `LoginView` already renders above
+            // this button — showing it a second time here would just
+            // duplicate the same message. Only a LOCAL, pre-network failure
+            // (decode error, user cancelled) is shown here.
+            if let localErrorMessage {
+                Text(localErrorMessage).zenithBodySmStyle(color: .zenithError)
+            }
+        }
+    }
+
+    private func handle(_ result: Result<ASAuthorization, Error>) {
+        switch result {
+        case .success(let authorization):
+            guard let credential = authorization.credential as? ASAuthorizationAppleIDCredential,
+                  let tokenData = credential.identityToken,
+                  let identityToken = String(data: tokenData, encoding: .utf8) else {
+                localErrorMessage = "Apple-Anmeldung fehlgeschlagen. Bitte erneut versuchen."
+                return
+            }
+            localErrorMessage = nil
+
+            // Only present on the account's very first authorization with
+            // this app — nil on every later sign-in, which is expected and
+            // fine (AuthAPI.appleSignIn/the backend both treat it as optional).
+            let fullName = credential.fullName.flatMap { components -> String? in
+                let formatted = PersonNameComponentsFormatter.localizedString(from: components, style: .default)
+                return formatted.isEmpty ? nil : formatted
+            }
+
+            isSigningIn = true
+            Task {
+                await appState.signInWithApple(identityToken: identityToken, fullName: fullName)
+                isSigningIn = false
+            }
+        case .failure(let error):
+            // The user cancelling the Apple Sign-In sheet also lands here
+            // (ASAuthorizationError.canceled) — that's expected, not a
+            // failure worth surfacing as an error.
+            if (error as? ASAuthorizationError)?.code == .canceled {
+                localErrorMessage = nil
+            } else {
+                localErrorMessage = error.localizedDescription
+            }
+        }
+    }
+}