fix(admin): surface errors from the pet-verify and warning mutations

Both had no onError handler, so a failed request (e.g. a permission
check) silently did nothing — the verify button looked broken with no
indication why. Now shows a toast on both success and failure.

src/app/p/[secret]/users/page.tsx

@@ -98,7 +98,13 @@ export default function AdminUsersPage() {
 
   const verifyMutation = useMutation(
     trpc.admin.setPetVerified.mutationOptions({
-      onSuccess: () => void qc.invalidateQueries({ queryKey: trpc.admin.listUsers.queryKey() }),
+      onSuccess: (pet) => {
+        void qc.invalidateQueries({ queryKey: trpc.admin.listUsers.queryKey() });
+        toast.success(pet.isVerified ? `${pet.name} verified.` : `${pet.name} un-verified.`);
+      },
+      onError: (err) => {
+        toast.error(`Verification failed: ${err.message}`);
+      },
     })
   );
 
@@ -118,6 +124,9 @@ export default function AdminUsersPage() {
         });
         setWarnReason("");
       },
+      onError: (err) => {
+        toast.error(`Warning failed: ${err.message}`);
+      },
     })
   );