Added Sign In with Apple

src/routes/auth/apple/+page.server.ts

@@ -0,0 +1,27 @@
+import { redirect } from '@sveltejs/kit';
+import type { Actions } from './$types';
+import { getAppleAuthUrl } from '$lib/server/apple-auth';
+import { encodeBase64url } from '@oslojs/encoding';
+
+export const actions: Actions = {
+	default: async ({ cookies, request }) => {
+		const data = await request.formData();
+		const anonymousId = data.get('anonymousId')?.toString() || '';
+
+		// Generate CSRF state
+		const stateBytes = crypto.getRandomValues(new Uint8Array(16));
+		const state = encodeBase64url(stateBytes);
+
+		// Store state + anonymousId in a short-lived cookie
+		// sameSite 'none' + secure required because Apple POSTs cross-origin
+		cookies.set('apple_oauth_state', JSON.stringify({ state, anonymousId }), {
+			path: '/',
+			httpOnly: true,
+			secure: true,
+			sameSite: 'none',
+			maxAge: 600
+		});
+
+		redirect(302, getAppleAuthUrl(state));
+	}
+};