Make expiryDate an internal concern, auto-set to event date + 7 days

The expiry date is no longer user-facing: it is removed from the API
(request and response) and the frontend. The backend now automatically
calculates it as the event date plus 7 days. The expired banner and
RSVP-bar filtering by expired status are also removed from the UI,
since expiry is purely an internal data-retention mechanism.

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

frontend/src/views/EventCreateView.vue

@@ -65,21 +65,6 @@
         <span v-if="errors.location" id="location-error" class="field-error" role="alert">{{ errors.location }}</span>
       </div>
 
-      <div class="form-group">
-        <label for="expiryDate" class="form-label">Expiry Date *</label>
-        <input
-          id="expiryDate"
-          v-model="form.expiryDate"
-          type="date"
-          class="form-field glass"
-          required
-          :min="tomorrow"
-          :aria-invalid="!!errors.expiryDate"
-          :aria-describedby="errors.expiryDate ? 'expiryDate-error' : undefined"
-        />
-        <span v-if="errors.expiryDate" id="expiryDate-error" class="field-error" role="alert">{{ errors.expiryDate }}</span>
-      </div>
-
       <button type="submit" class="btn-primary glass" :disabled="submitting">
         {{ submitting ? 'Creating…' : 'Create Event' }}
       </button>
@@ -90,7 +75,7 @@
 </template>
 
 <script setup lang="ts">
-import { reactive, ref, computed, watch } from 'vue'
+import { reactive, ref, watch } from 'vue'
 import { RouterLink, useRouter } from 'vue-router'
 import { api } from '@/api/client'
 import { useEventStorage } from '@/composables/useEventStorage'
@@ -103,7 +88,6 @@ const form = reactive({
   description: '',
   dateTime: '',
   location: '',
-  expiryDate: '',
 })
 
 const errors = reactive({
@@ -111,31 +95,22 @@ const errors = reactive({
   description: '',
   dateTime: '',
   location: '',
-  expiryDate: '',
 })
 
 const submitting = ref(false)
 const serverError = ref('')
 
-const tomorrow = computed(() => {
-  const d = new Date()
-  d.setDate(d.getDate() + 1)
-  return d.toISOString().split('T')[0]
-})
-
 function clearErrors() {
   errors.title = ''
   errors.description = ''
   errors.dateTime = ''
   errors.location = ''
-  errors.expiryDate = ''
   serverError.value = ''
 }
 
 // Clear individual field errors when the user types
 watch(() => form.title, () => { errors.title = ''; serverError.value = '' })
 watch(() => form.dateTime, () => { errors.dateTime = ''; serverError.value = '' })
-watch(() => form.expiryDate, () => { errors.expiryDate = ''; serverError.value = '' })
 watch(() => form.description, () => { serverError.value = '' })
 watch(() => form.location, () => { serverError.value = '' })
 
@@ -153,14 +128,6 @@ function validate(): boolean {
     valid = false
   }
 
-  if (!form.expiryDate) {
-    errors.expiryDate = 'Expiry date is required.'
-    valid = false
-  } else if (form.expiryDate <= (new Date().toISOString().split('T')[0] ?? '')) {
-    errors.expiryDate = 'Expiry date must be in the future.'
-    valid = false
-  }
-
   return valid
 }
 
@@ -186,7 +153,6 @@ async function handleSubmit() {
         dateTime: dateTimeWithOffset,
         timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
         location: form.location.trim() || undefined,
-        expiryDate: form.expiryDate,
       },
     })
 
@@ -212,7 +178,6 @@ async function handleSubmit() {
         organizerToken: data.organizerToken,
         title: data.title,
         dateTime: data.dateTime,
-        expiryDate: data.expiryDate,
       })
 
       router.push({ name: 'event', params: { eventToken: data.eventToken } })