feat(onboarding): add A2 household setup page with responsive progress sidebar layout

Desktop: 300px ProgressSidebar (step 1 active) + flex form area.
Mobile: "Schritt 1 von 3" eyebrow + HouseholdSetupForm.
Also stubs /household/staples as redirect target for A3.

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

frontend/src/routes/household/setup/page.test.ts

@@ -0,0 +1,53 @@
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/svelte';
+import Page from './+page.svelte';
+
+vi.mock('$app/forms', () => ({
+	enhance: () => ({ destroy: () => {} })
+}));
+
+describe('household setup page', () => {
+	it('renders the form heading', () => {
+		render(Page);
+		expect(screen.getByText('Haushalt benennen')).toBeInTheDocument();
+	});
+
+	it('renders the household name input', () => {
+		render(Page);
+		expect(screen.getByLabelText('Haushaltsname')).toBeInTheDocument();
+	});
+
+	it('renders the continue button', () => {
+		render(Page);
+		expect(screen.getByRole('button', { name: /weiter/i })).toBeInTheDocument();
+	});
+
+	it('renders the ProgressSidebar with step 1 active', () => {
+		render(Page);
+		const step1 = screen.getByTestId('step-1');
+		expect(step1).toHaveAttribute('aria-current', 'step');
+	});
+
+	it('renders steps 2 and 3 as future steps', () => {
+		render(Page);
+		expect(screen.getByTestId('step-2')).not.toHaveAttribute('aria-current');
+		expect(screen.getByTestId('step-3')).not.toHaveAttribute('aria-current');
+	});
+
+	it('does not render app navigation chrome', () => {
+		render(Page);
+		// No nav links like Planer or Rezepte (those are app shell nav items)
+		expect(screen.queryByText('Planer')).not.toBeInTheDocument();
+		expect(screen.queryByText('Rezepte')).not.toBeInTheDocument();
+	});
+
+	it('sets the page title', () => {
+		render(Page);
+		expect(document.title).toBe('Haushalt einrichten — Mealplan');
+	});
+
+	it('renders the mobile step indicator text', () => {
+		render(Page);
+		expect(screen.getByText(/schritt 1 von 3/i)).toBeInTheDocument();
+	});
+});