fix: refresh assignable persons list after assignment and keep dialog open

Invalidate assignable-persons query cache in useAssignPersonToShift
onSuccess so the list reflects the new assignment immediately. Keep the
dialog open after assigning a person to allow sequential assignments,
showing a brief success snackbar instead of closing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/app/src/components/shifts/AssignPersonDialog.vue

@@ -26,6 +26,8 @@ const searchQuery = ref('')
 const showOnlyAvailable = ref(true)
 const selectedCrowdType = ref<string | null>(null)
 const assignError = ref<string | null>(null)
+const showSuccess = ref(false)
+const successName = ref('')
 
 // Clear error on filter changes
 watch([searchQuery, showOnlyAvailable, selectedCrowdType], () => {
@@ -111,7 +113,8 @@ async function handleAssign(person: AssignablePerson) {
       personId: person.id,
     })
     emit('assigned')
-    modelValue.value = false
+    successName.value = person.name
+    showSuccess.value = true
   }
   catch (error: any) {
     const message = error.response?.data?.errors?.person_id?.[0]
@@ -348,4 +351,12 @@ async function handleAssign(person: AssignablePerson) {
       </VCardActions>
     </VCard>
   </VDialog>
+
+  <VSnackbar
+    v-model="showSuccess"
+    color="success"
+    :timeout="2000"
+  >
+    {{ successName }} toegewezen
+  </VSnackbar>
 </template>

apps/app/src/composables/api/useShiftAssignments.ts

@@ -140,6 +140,7 @@ export function useAssignPersonToShift(eventId: Ref<string>) {
     },
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['shift-assignments', eventId.value] })
+      queryClient.invalidateQueries({ queryKey: ['assignable-persons'] })
       queryClient.invalidateQueries({ queryKey: ['shifts'] })
       queryClient.invalidateQueries({ queryKey: ['persons', eventId.value] })
     },