feat: add donations feature with one-time payments - M6 (refs #55)

frontend/src/features/subscription/hooks/useSubscription.ts

@@ -91,3 +91,27 @@ export const useDowngrade = () => {
     },
   });
 };
+
+export const useCreateDonation = () => {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (amount: number) => subscriptionApi.createDonation(amount),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['donations'] });
+    },
+    onError: (error: unknown) => {
+      const err = error as { response?: { data?: { error?: string } } };
+      toast.error(err.response?.data?.error || 'Donation failed');
+    },
+  });
+};
+
+export const useDonations = () => {
+  const { isAuthenticated, isLoading } = useAuth0();
+  return useQuery({
+    queryKey: ['donations'],
+    queryFn: () => subscriptionApi.getDonations(),
+    enabled: isAuthenticated && !isLoading,
+    staleTime: 5 * 60 * 1000,
+  });
+};