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/EmptyState.vue

@@ -0,0 +1,31 @@
+<template>
+  <div class="empty-state">
+    <p class="empty-state__message">No events yet.<br />Create your first one!</p>
+    <RouterLink to="/create" class="btn-primary empty-state__cta">+ Create Event</RouterLink>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { RouterLink } from 'vue-router'
+</script>
+
+<style scoped>
+.empty-state {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: var(--spacing-lg);
+}
+
+.empty-state__message {
+  font-size: 1rem;
+  font-weight: 400;
+  color: var(--color-text-on-gradient);
+  opacity: 0.9;
+  text-align: center;
+}
+
+.empty-state__cta {
+  max-width: 280px;
+}
+</style>