fix: conform moved code to eslint indent/quotes, 4-arg mutation callbacks

- eslint --fix on branch-changed backend files (indent shift from the
  module-wrapper nesting in decomposed files); backend lint now 904
  errors vs 1,315 on main
- useMutationWithToast forwards all four TanStack v5 callback args
  (tsc -b strict build flagged the 3-arg passthrough)

frontend/src/hooks/useMutationWithToast.ts

@@ -47,7 +47,7 @@ export function useMutationWithToast<
 
   return useMutation<TData, TError, TVariables, TContext>({
     ...mutationOptions,
-    onSuccess: (data, variables, context) => {
+    onSuccess: (data, variables, onMutateResult, context) => {
       invalidateKeys?.forEach((queryKey) => {
         queryClient.invalidateQueries({ queryKey });
       });
@@ -56,9 +56,9 @@ export function useMutationWithToast<
           typeof successMessage === 'function' ? successMessage(data, variables) : successMessage
         );
       }
-      onSuccess?.(data, variables, context);
+      onSuccess?.(data, variables, onMutateResult, context);
     },
-    onError: (error, variables, context) => {
+    onError: (error, variables, onMutateResult, context) => {
       const message =
         typeof errorMessage === 'function'
           ? errorMessage(error)
@@ -67,7 +67,7 @@ export function useMutationWithToast<
             (error instanceof Error ? error.message : undefined) ||
             'An unexpected error occurred';
       toast.error(message);
-      onError?.(error, variables, context);
+      onError?.(error, variables, onMutateResult, context);
     },
   });
 }