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/invites/+server.ts

@@ -0,0 +1,9 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { apiClient } from '$lib/server/api';
+
+export const POST: RequestHandler = async ({ fetch }) => {
+	const api = apiClient(fetch);
+	const { data, response } = await api.POST('/v1/households/mine/invites');
+	return json(data, { status: response?.status ?? 201 });
+};