feat(bookings): allow cancelling booking confirmations

Add API endpoint to revert confirmed bookings to pending status
Add unconfirm buttons to the bookings list and confirmation page
Update inventory summary when a confirmation is cancelled

app/pages/confirmation/[token].vue

@@ -1,5 +1,5 @@
 <script lang="ts" setup>
-import type { ConfirmBookingResponse, PublicBooking } from '~~/shared/booking'
+import type { CancelBookingConfirmationResponse, ConfirmBookingResponse, PublicBooking } from '~~/shared/booking'
 
 import {
   formatBookingCurrency,
@@ -15,6 +15,7 @@ const apiClient = useApiClient()
 
 const token = String(route.params.token || '')
 const confirming = ref(false)
+const cancelling = ref(false)
 
 let initialBooking: PublicBooking
 
@@ -114,6 +115,47 @@ async function confirmBooking() {
     confirming.value = false
   }
 }
+
+async function cancelBookingConfirmation() {
+  if (booking.value.status !== 'confirmed') {
+    return
+  }
+
+  if (import.meta.client && !window.confirm('Cancel this confirmation? The booking will return to pending and the seats will be released.')) {
+    return
+  }
+
+  cancelling.value = true
+
+  try {
+    const response = await apiClient<CancelBookingConfirmationResponse>(
+      `/api/public/bookings/${token}/cancel`,
+      {
+        method: 'POST'
+      }
+    )
+
+    booking.value = response.booking
+
+    toast.add({
+      title: response.alreadyPending ? 'Booking already pending' : 'Confirmation cancelled',
+      description: response.alreadyPending
+        ? 'This booking was already pending confirmation.'
+        : 'The booking has been returned to pending status.',
+      color: response.alreadyPending ? 'warning' : 'success',
+      icon: 'i-lucide-x-circle'
+    })
+  } catch (error) {
+    toast.add({
+      title: 'Cancellation failed',
+      description: getErrorMessage(error, 'Please try again in a moment.'),
+      color: 'error',
+      icon: 'i-lucide-circle-alert'
+    })
+  } finally {
+    cancelling.value = false
+  }
+}
 </script>
 
 <template>
@@ -198,13 +240,24 @@ async function confirmBooking() {
           />
 
           <UButton
+            v-if="booking.status === 'pending'"
             label="Confirm This Booking"
             icon="i-lucide-check-check"
             class="justify-center"
-            :disabled="booking.status === 'confirmed'"
             :loading="confirming"
             @click="confirmBooking"
           />
+
+          <UButton
+            v-else
+            label="Cancel Confirmation"
+            color="error"
+            variant="outline"
+            icon="i-lucide-x-circle"
+            class="justify-center"
+            :loading="cancelling"
+            @click="cancelBookingConfirmation"
+          />
         </div>
       </UCard>
     </div>