🔦 Use COOLDOWN defines for paramedic penlights

Uses the new COOLDOWN_ defines for the penlight's cooldown, which
functions exactly the same as the `world.time` code, but is slightly
cleaner and less prone to mistakes.

code/datums/wounds/burns.dm

@@ -249,7 +249,7 @@
 
 /// Paramedic UV penlights
 /datum/wound/burn/proc/uv(obj/item/flashlight/pen/paramedic/I, mob/user)
-	if(I.uv_cooldown > world.time)
+	if(!COOLDOWN_FINISHED(I, uv_cooldown))
 		to_chat(user, "<span class='notice'>[I] is still recharging!</span>")
 		return
 	if(infestation <= 0 || infestation < sanitization)
@@ -258,7 +258,7 @@
 
 	user.visible_message("<span class='notice'>[user] flashes the burns on [victim]'s [limb] with [I].</span>", "<span class='notice'>You flash the burns on [user == victim ? "your" : "[victim]'s"] [limb.name] with [I].</span>", vision_distance=COMBAT_MESSAGE_RANGE)
 	sanitization += I.uv_power
-	I.uv_cooldown = world.time + I.uv_cooldown_length
+	COOLDOWN_START(I, uv_cooldown, I.uv_cooldown_length)
 
 /datum/wound/burn/treat(obj/item/I, mob/user)
 	if(istype(I, /obj/item/stack/medical/gauze))

code/game/objects/items/devices/flashlight.dm

@@ -188,7 +188,7 @@
 	desc = "A high-powered UV penlight intended to help stave off infection in the field on serious burned patients. Probably really bad to look into."
 	icon_state = "penlight_surgical"
 	/// Our current UV cooldown
-	var/uv_cooldown = 0
+	COOLDOWN_DECLARE(uv_cooldown)
 	/// How long between UV fryings
 	var/uv_cooldown_length = 1 MINUTES
 	/// How much sanitization to apply to the burn wound