appview/settings: prevent domain claims shorter than 4 chars

🤑📈

Signed-off-by: Anirudh Oppiliappan <[e-mail]>

appview/settings/settings.go

···
 		return
 	}
 
+	if len(subdomain) < 4 {
+		s.Pages.Notice(w, "settings-sites-error", "Subdomain must be at least 4 characters long.")
+		return
+	}
+
 	if !isValidSubdomain(subdomain) {
 		s.Pages.Notice(w, "settings-sites-error", "Invalid subdomain. Use only lowercase letters, digits, and hyphens. Cannot start or end with a hyphen.")
 		return