Fixes some atom health bugs (#22312)

## About PR
- Fixes #22260
- Fixes #22304
- Fixes #22234

Additionally changes some health values for:

- Canisters, `50` -> `100`. Takes 5 crowbar hits to break instead of 3,
these shouldn't break so easily
- Railings, `30` -> `75`. 3 crowbars instead of 1
- Reinforced girders, `600` -> `300`. Still takes a lot of crowbars
before breaking, barebone girders shouldn't compete reinforced walls

code/game/objects/structures/displaycase.dm

@@ -11,6 +11,8 @@
 	var/obj/held_obj
 	var/open = FALSE
 	var/destroyed = FALSE
+	hitsound = 'sound/effects/glass_hit.ogg'
+	destroy_sound = SFX_BREAK_GLASS
 	var/spawn_contained_type
 
 /obj/structure/displaycase/Initialize(mapload)
@@ -23,15 +25,14 @@
 /obj/structure/displaycase/ex_act(severity)
 	switch(severity)
 		if (1)
-			do_destroy()
+			on_death()
 		if (2)
 			if(prob(50))
-				health -= 15
-				health_check()
+				on_death()
+			else
+				add_damage(rand(20, 50))
 		if (3)
-			if(prob(50))
-				health -= 5
-				health_check()
+			add_damage(rand(10, 40))
 
 
 /obj/structure/displaycase/bullet_act(obj/projectile/hitting_projectile, def_zone, piercing_hit)
@@ -39,21 +40,15 @@
 	if(. != BULLET_ACT_HIT)
 		return .
 
-	health -= hitting_projectile.get_structure_damage()
-	health_check()
+	var/damage = hitting_projectile.damage
+	if(damage)
+		add_damage(damage)
 
-/obj/structure/displaycase/proc/health_check()
-	if(health <= 0)
-		do_destroy()
-	else
-		playsound(loc, 'sound/effects/glass_hit.ogg', 75, 1)
-
-/obj/structure/displaycase/proc/do_destroy()
+/obj/structure/displaycase/on_death()
 	if(!destroyed)
 		density = FALSE
 		destroyed = TRUE
 		new /obj/item/material/shard(loc)
-		playsound(src, SFX_BREAK_GLASS, 70, 1)
 		update_icon()
 
 /obj/structure/displaycase/update_icon()
@@ -69,30 +64,33 @@
 		underlays += I
 
 /obj/structure/displaycase/attackby(obj/item/attacking_item, mob/user)
-	user.setClickCooldown(DEFAULT_ATTACK_COOLDOWN)
 	if(istype(attacking_item, /obj/item/card/id))
 		if(destroyed)
 			to_chat(user, SPAN_WARNING("\The [src] has been destroyed and cannot be unlocked."))
 			return
+
 		var/obj/item/card/id/ID = attacking_item
 		if(check_access(ID))
 			user.visible_message("<b>[user]</b> presses their ID against \the [src], [open ? "closing" : "opening"] it.", SPAN_NOTICE("You press your ID against \the [src], [open ? "closing" : "opening"] it."))
 			open = !open
 			update_icon()
+
 		else
 			to_chat(user, SPAN_WARNING("Access denied."))
+
+		return
+
 	else if(!held_obj && (destroyed || open))
 		to_chat(user, SPAN_NOTICE("You set \the [attacking_item] down on \the [src]."))
 		user.drop_from_inventory(attacking_item, src)
 		held_obj = attacking_item
 		update_icon()
-	else
-		if(destroyed)
-			to_chat(user, SPAN_WARNING("\The [src] has already been destroyed."))
-			return
-		health -= attacking_item.force
-		health_check()
-		return ..()
+
+	if(destroyed)
+		to_chat(user, SPAN_WARNING("\The [src] has already been destroyed."))
+		return
+
+	. = ..()
 
 /obj/structure/displaycase/attack_hand(mob/user)
 	user.setClickCooldown(DEFAULT_ATTACK_COOLDOWN)
@@ -112,8 +110,9 @@
 				to_chat(user, SPAN_NOTICE("You peer inside \the [src], noticing it has nothing inside."))
 		else
 			user.visible_message("<b>[user]</b> kicks \the [src].", SPAN_WARNING("You kick \the [src]."))
-			health -= 2
-			health_check()
+			user.do_attack_animation(src)
+			playsound(src, 'sound/effects/glass_hit.ogg', 50, 1)
+			add_damage(3)
 
 /obj/structure/displaycase/captain_laser
 	spawn_contained_type = /obj/item/gun/energy/captain