fix: ensure appointment is created before saving claim from claims page

- mutationFn now throws on non-ok responses so failed appointment
  creation (409 no slots, 400 validation) properly rejects instead of
  silently calling onSuccess with no id
- handleAppointmentSubmit rejects if server returns success but no id
- invalidate QK_APPOINTMENTS_BASE cache after successful appointment
  creation so the appointments page refreshes automatically

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

apps/Frontend/src/pages/claims-page.tsx

@@ -113,9 +113,14 @@ export default function ClaimsPage() {
         "/api/appointments/upsert",
         appointment
       );
-      return await res.json();
+      const data = await res.json();
+      if (!res.ok) {
+        throw new Error(data?.message || "Failed to create appointment");
+      }
+      return data;
     },
     onSuccess: (appointment) => {
+      queryClient.invalidateQueries({ queryKey: QK_APPOINTMENTS_BASE });
       toast({
         title: "Appointment Scheduled",
         description: appointment.message || "Appointment created successfully.",
@@ -319,14 +324,13 @@ export default function ClaimsPage() {
         },
         {
           onSuccess: (appointment) => {
+            if (!appointment?.id) {
+              reject(new Error("Appointment was created but returned no ID"));
+              return;
+            }
             resolve(appointment.id);
           },
           onError: (error) => {
-            toast({
-              title: "Error",
-              description: "Could not schedule appointment",
-              variant: "destructive",
-            });
             reject(error);
           },
         }