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/routes/(app)/members/[userId]/server.test.ts

@@ -0,0 +1,50 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+vi.mock('$env/dynamic/private', () => ({ env: { BACKEND_URL: 'http://localhost:8080' } }));
+
+const mockDelete = vi.fn();
+const mockPatch = vi.fn();
+vi.mock('$lib/server/api', () => ({
+	apiClient: () => ({ DELETE: mockDelete, PATCH: mockPatch })
+}));
+
+const USER_UUID = '22222222-2222-2222-2222-222222222222';
+
+describe('members server routes', () => {
+	let DELETE: any;
+	let PATCH: any;
+
+	beforeEach(async () => {
+		mockDelete.mockReset();
+		mockPatch.mockReset();
+		vi.resetModules();
+		const mod = await import('./+server');
+		DELETE = mod.DELETE;
+		PATCH = mod.PATCH;
+	});
+
+	it('DELETE proxies to backend and returns 204', async () => {
+		mockDelete.mockResolvedValue({ response: { status: 204 } });
+		const event = {
+			fetch: vi.fn(),
+			params: { userId: USER_UUID },
+			request: { json: vi.fn() }
+		} as any;
+		const res = await DELETE(event);
+		expect(res.status).toBe(204);
+	});
+
+	it('PATCH proxies to backend and returns member response', async () => {
+		mockPatch.mockResolvedValue({
+			data: { status: 'success', data: { userId: USER_UUID, displayName: 'Tom', role: 'planner', joinedAt: '' } },
+			response: { status: 200 }
+		});
+		const event = {
+			fetch: vi.fn(),
+			params: { userId: USER_UUID },
+			request: { json: async () => ({ role: 'planner' }) }
+		} as any;
+		const res = await PATCH(event);
+		expect(res.status).toBe(200);
+	});
+});