fix: user not been able to add new user on langflow docker (#3538)

🐛 (use-post-add-user.ts): fix API endpoint URL to include trailing slash for consistency and to ensure correct routing

src/frontend/src/controllers/API/queries/auth/use-post-add-user.ts

@@ -13,7 +13,7 @@ export const useAddUser: useMutationFunctionType<undefined, UserInputType> = (
   const addUserFunction = async (
     user: UserInputType,
   ): Promise<Array<Users>> => {
-    const res = await api.post(`${getURL("USERS")}`, user);
+    const res = await api.post(`${getURL("USERS")}/`, user);
     return res.data;
   };