Removes a ton of unused tablet vars, re-organizes the rest (#70344)

* Removes a ton of unused vars, re-organizes the rest

Removes a ton of unused vars from Modular computers
Re-organizes the rest, and adds autodoc comments to most of them
Moved 2 vars (saved_image and invisible) from the tablet to the messenger app, since that's where it was used. I didn't see the point of having these vars be on every computer anyways, only PDAs have the app.
Renames Clown's honk virus var
Makes Messenger app's saved image, actually used.

* static list and NODECONSTRUCT_1 check

* oops

code/modules/modular_computers/computers/item/computer_ui.dm

@@ -40,8 +40,8 @@
 		to_chat(user, span_danger("\The [src] beeps three times, it's screen displaying a \"DISK ERROR\" warning."))
 		return // No HDD, No HDD files list or no stored files. Something is very broken.
 
-	if(honkamnt > 0) // EXTRA annoying, huh!
-		honkamnt--
+	if(honkvirus_amount > 0) // EXTRA annoying, huh!
+		honkvirus_amount--
 		playsound(src, 'sound/items/bikehorn.ogg', 30, TRUE)
 
 	ui = SStgui.try_update_ui(user, src, ui)
@@ -59,8 +59,6 @@
 
 	return data
 
-
-
 /obj/item/modular_computer/ui_data(mob/user)
 	var/list/data = get_header_data()
 	data["device_theme"] = device_theme