feat: add dashboard layout with navigation and auth guard

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/routes/dashboard/+layout.server.ts

@@ -0,0 +1,11 @@
+import { redirect } from '@sveltejs/kit';
+import type { LayoutServerLoad } from './$types';
+
+export const load: LayoutServerLoad = async ({ locals }) => {
+	if (!locals.user) {
+		redirect(307, '/login');
+	}
+	return {
+		user: locals.user
+	};
+};