feat(members): implement /members page — Kachel-Ansicht (E2, issue #48)

Backend:
- Rename V006 migration to V026 (avoid conflict with existing V006)
- Migration adds invalidated_at + partial unique index on household_invite

Frontend:
- Toast.svelte — new system component (message + dismiss)
- SegmentedControl.svelte — new system component (options, value, onchange)
- members/+page.server.ts — loads members + active invite
- members/[userId]/+server.ts — DELETE/PATCH proxy
- members/invites/+server.ts — POST (regenerate) proxy
- MemberCard.svelte — tile with avatar, kebab, inline role edit
- RemoveDialog.svelte — confirmation dialog (desktop modal + BottomSheet mobile)
- InviteCard.svelte + InvitePanel.svelte — invite management UI
- MemberGrid.svelte — responsive 4/2-col grid with sorted members
- members/+page.svelte — page composing all components with optimistic updates

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

frontend/src/lib/components/SegmentedControl.test.ts

@@ -0,0 +1,30 @@
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/svelte';
+import userEvent from '@testing-library/user-event';
+import SegmentedControl from './SegmentedControl.svelte';
+
+const options = [
+	{ value: 'planner', label: 'Planer' },
+	{ value: 'member', label: 'Mitglied' }
+];
+
+describe('SegmentedControl', () => {
+	it('renders all option labels', () => {
+		render(SegmentedControl, { props: { options, value: 'planner', onchange: vi.fn() } });
+		expect(screen.getByRole('button', { name: 'Planer' })).toBeInTheDocument();
+		expect(screen.getByRole('button', { name: 'Mitglied' })).toBeInTheDocument();
+	});
+
+	it('marks the active option with aria-pressed', () => {
+		render(SegmentedControl, { props: { options, value: 'planner', onchange: vi.fn() } });
+		expect(screen.getByRole('button', { name: 'Planer' })).toHaveAttribute('aria-pressed', 'true');
+		expect(screen.getByRole('button', { name: 'Mitglied' })).toHaveAttribute('aria-pressed', 'false');
+	});
+
+	it('calls onchange with the new value when an option is clicked', async () => {
+		const onchange = vi.fn();
+		render(SegmentedControl, { props: { options, value: 'planner', onchange } });
+		await userEvent.click(screen.getByRole('button', { name: 'Mitglied' }));
+		expect(onchange).toHaveBeenCalledWith('member');
+	});
+});