fix login confusion and enforce reactive subscription after login

frontend/src/lib/components/AuthShell.svelte

@@ -4,11 +4,13 @@
 	let {
 		title,
 		subtitle,
-		children
+		children,
+		secondary
 	}: {
 		title: string;
 		subtitle?: string;
 		children?: any;
+		secondary?: any;
 	} = $props();
 </script>
 
@@ -21,6 +23,9 @@
 		{/if}
 		{@render children?.()}
 	</div>
+	{#if secondary}
+		<div class="card secondary">{@render secondary?.()}</div>
+	{/if}
 </main>
 
 <style>
@@ -64,6 +69,9 @@
 		font-size: 0.9rem;
 		line-height: 1.5;
 	}
+	.card.secondary {
+		margin-top: 1rem;
+	}
 	@media (max-width: 480px) {
 		.card {
 			padding: 1.5rem;