Is the ejaculation that occurred immediately upon waking up after seeing something sexually arousing, and which was not intentional, considered forbidden masturbation or permissible wet dream, and will one be punished for it on the Day of Judgment, given the recurrence of wet dreams?

What you mentioned about a wet dream (ihtilam) is not considered masturbation, and there is no sin in it, unless you intervened to expel semen after waking up. A wet dream is a natural occurrence for unmarried youth. We advise you to fear Allah and to marry if you are able, as the Prophet, peace and blessings be upon him, said: "O young men, whoever among you can afford to marry, let him do so, for it helps him lower his gaze and guard his chastity. And whoever cannot afford it, let him fast, for it will be a shield for him."