Refactor /obj/screen to /atom/movable/screen (#19852)

Part of backend stuff required for #19188. Should probably be test
merged.

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Co-authored-by: Cody Brittain <cbrittain10@live.com>

code/modules/paperwork/clipboard.dm

@@ -22,7 +22,7 @@
 /obj/item/clipboard/MouseDrop(obj/over_object as obj) //Quick clipboard fix. -Agouri
 	if(ishuman(usr))
 		var/mob/M = usr
-		if(!(istype(over_object, /obj/screen) ))
+		if(!(istype(over_object, /atom/movable/screen) ))
 			return ..()
 
 		if(!M.restrained() && !M.stat)

code/modules/paperwork/photography.dm

@@ -113,7 +113,7 @@ var/global/photo_count = 0
 
 	if((istype(usr, /mob/living/carbon/human)))
 		var/mob/M = usr
-		if(!( istype(over_object, /obj/screen) ))
+		if(!( istype(over_object, /atom/movable/screen) ))
 			return ..()
 		playsound(loc, /singleton/sound_category/rustle_sound, 50, 1, -5)
 		if((!( M.restrained() ) && !( M.stat ) && M.back == src))