Implement event creation frontend (EventCreateView)

Form with client-side validation, server error handling, aria-invalid/
aria-describedby for a11y, localStorage persistence via useEventStorage
composable. Routes for /create and /events/:token.

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

frontend/src/composables/useEventStorage.ts

@@ -0,0 +1,41 @@
+export interface StoredEvent {
+  eventToken: string
+  organizerToken?: string
+  title: string
+  dateTime: string
+  expiryDate: string
+}
+
+const STORAGE_KEY = 'fete:events'
+
+function readEvents(): StoredEvent[] {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY)
+    return raw ? (JSON.parse(raw) as StoredEvent[]) : []
+  } catch {
+    return []
+  }
+}
+
+function writeEvents(events: StoredEvent[]): void {
+  localStorage.setItem(STORAGE_KEY, JSON.stringify(events))
+}
+
+export function useEventStorage() {
+  function saveCreatedEvent(event: StoredEvent): void {
+    const events = readEvents().filter((e) => e.eventToken !== event.eventToken)
+    events.push(event)
+    writeEvents(events)
+  }
+
+  function getStoredEvents(): StoredEvent[] {
+    return readEvents()
+  }
+
+  function getOrganizerToken(eventToken: string): string | undefined {
+    const event = readEvents().find((e) => e.eventToken === eventToken)
+    return event?.organizerToken
+  }
+
+  return { saveCreatedEvent, getStoredEvents, getOrganizerToken }
+}