fix(auth): use dynamic imports for @simplewebauthn/browser to fix SSR (#43)

The @simplewebauthn/browser package is browser-only and cannot be
imported at the module level in SvelteKit components that undergo SSR.
Replace static imports with dynamic import() inside onMount callbacks
to ensure the package is only loaded client-side.

Fixes the /auth/login 500 error on the tinyland deployment.

Author: Jesssullivan

app/src/lib/components/auth/PasskeyManager.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { browserSupportsWebAuthn, startRegistration } from '@simplewebauthn/browser';
+	import { onMount } from 'svelte';
 
 	let { authMethod = 'oauth' }: { authMethod: string } = $props();
 
@@ -15,8 +15,11 @@
 	let loading = $state(true);
 	let registering = $state(false);
 	let error = $state('');
+	let webauthnSupported = $state(false);
 
-	$effect(() => {
+	onMount(async () => {
+		const { browserSupportsWebAuthn } = await import('@simplewebauthn/browser');
+		webauthnSupported = browserSupportsWebAuthn();
 		loadPasskeys();
 	});
 
@@ -38,6 +41,8 @@
 		registering = true;
 		error = '';
 		try {
+			const { startRegistration } = await import('@simplewebauthn/browser');
+
 			const optionsRes = await fetch('/auth/webauthn/register');
 			if (!optionsRes.ok) {
 				throw new Error('Failed to get registration options');
@@ -87,7 +92,7 @@
 		});
 	}
 
-	const canRegister = $derived(authMethod === 'oauth' && browserSupportsWebAuthn());
+	const canRegister = $derived(authMethod === 'oauth' && webauthnSupported);
 </script>
 
 <div class="space-y-3">

app/src/routes/auth/login/+page.svelte

@@ -1,18 +1,21 @@
 <script lang="ts">
-	import { browserSupportsWebAuthn, startAuthentication } from '@simplewebauthn/browser';
+	import { onMount } from 'svelte';
 
 	let webauthnSupported = $state(false);
 	let webauthnLoading = $state(false);
 	let webauthnError = $state('');
 
-	$effect(() => {
+	onMount(async () => {
+		const { browserSupportsWebAuthn } = await import('@simplewebauthn/browser');
 		webauthnSupported = browserSupportsWebAuthn();
 	});
 
 	async function loginWithPasskey() {
 		webauthnLoading = true;
 		webauthnError = '';
 		try {
+			const { startAuthentication } = await import('@simplewebauthn/browser');
+
 			const optionsRes = await fetch('/auth/webauthn/authenticate');
 			const options = await optionsRes.json();