Add event list feature (009-list-events)

Enable users to see all their saved events on the home screen, sorted
by date with upcoming events first. Key capabilities:

- EventCard with title, relative time display, and organizer/attendee
  role badge
- Sortable EventList with past-event visual distinction (faded style)
- Empty state when no events are stored
- Swipe-to-delete gesture with confirmation dialog
- Floating action button for quick event creation
- Rename router param :token → :eventToken across all views
- useRelativeTime composable (Intl.RelativeTimeFormat)
- useEventStorage: add validation, removeEvent(), reactive versioning
- Full E2E and unit test coverage for all new components

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

frontend/src/components/__tests__/EmptyState.spec.ts

@@ -0,0 +1,35 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { createRouter, createMemoryHistory } from 'vue-router'
+import EmptyState from '../EmptyState.vue'
+
+const router = createRouter({
+  history: createMemoryHistory(),
+  routes: [
+    { path: '/', component: { template: '<div />' } },
+    { path: '/create', name: 'create', component: { template: '<div />' } },
+  ],
+})
+
+function mountEmptyState() {
+  return mount(EmptyState, {
+    global: {
+      plugins: [router],
+    },
+  })
+}
+
+describe('EmptyState', () => {
+  it('renders an inviting message', () => {
+    const wrapper = mountEmptyState()
+    expect(wrapper.text()).toContain('No events yet')
+  })
+
+  it('renders a Create Event link', () => {
+    const wrapper = mountEmptyState()
+    const link = wrapper.find('a')
+    expect(link.exists()).toBe(true)
+    expect(link.text()).toContain('Create Event')
+    expect(link.attributes('href')).toBe('/create')
+  })
+})