Container cleanup, standalone security panel (#20909)

Updated crate and locker sprites and icon overlay code to use a new
standalone 'securitypanel' overlay to lay the groundwork for, in the
future, being able to install/uninstall access-code locks on containers
just like you can in airlocks. For lockers, little visual change at all.
For crates, the security panel is now an overlay within the 'handle'
section of the crate rather than being a chunky box off to the side on
front. Locked/unlocked/emag sprites also updated for the new panel
location.
![Screenshot 2025-06-28
130646](https://github.com/user-attachments/assets/4b4469e7-5d62-42e0-9d9b-27c2f70a4239)
![Screenshot 2025-06-28
130944](https://github.com/user-attachments/assets/5741094f-9214-435a-8ef1-97e5c06b1c61)
![Screenshot 2025-06-28
130951](https://github.com/user-attachments/assets/3d9563b5-a89c-407d-9f8b-190d6382fb8b)

Moved closet.dmi, crate.dmi, guncabinet.dmi, safe.dmi, and
walllocker.dmi to a new subfolder /icons/obj/containers, and updated all
references to them in code, for sake of organization. Ideally (IMHO),
we'd differentiate structure-based storage containers from item-based
storage containers, but that's a larger organizational task and outside
of scope- this just moves storage structures into one common location.

Deleted sciguncabinet.dmi, as its contents had already been migrated to
guncabinet.dmi and it was no longer referenced anywhere in the codebase.

code/game/objects/structures/crates_lockers/closets.dm

@@ -1,7 +1,7 @@
 /obj/structure/closet
 	name = "closet"
 	desc = "It's a basic storage unit."
-	icon = 'icons/obj/closet.dmi'
+	icon = 'icons/obj/containers/closet.dmi'
 	icon_state = "generic"
 	density = TRUE
 	build_amt = 2
@@ -626,6 +626,7 @@
 			update_secure_overlays()
 
 /obj/structure/closet/proc/update_secure_overlays()
+	AddOverlays("[icon_door_overlay]securitypanel")
 	if(broken)
 		AddOverlays("[icon_door_overlay]emag")
 	else

code/game/objects/structures/crates_lockers/closets/secure/guncabinet.dm

@@ -1,7 +1,7 @@
 /obj/structure/closet/secure_closet/guncabinet
 	name = "gun cabinet"
 	req_access = list(ACCESS_ARMORY)
-	icon = 'icons/obj/guncabinet.dmi'
+	icon = 'icons/obj/containers/guncabinet.dmi'
 	icon_state = "base"
 	anchored = TRUE
 	canbemoved = TRUE

code/game/objects/structures/crates_lockers/closets/secure/locker.dm

@@ -1,7 +1,7 @@
 /obj/structure/closet/secure_closet
 	name = "locker"
 	desc = "It's a steel ID-locked locker."
-	icon = 'icons/obj/closet.dmi'
+	icon = 'icons/obj/containers/closet.dmi'
 	icon_state = "secure"
 	anchored = FALSE
 	secure = TRUE

code/game/objects/structures/crates_lockers/closets/walllocker.dm

@@ -4,7 +4,7 @@
 /obj/structure/closet/walllocker
 	name = "wall locker"
 	desc = "A wall mounted storage locker."
-	icon = 'icons/obj/walllocker.dmi'
+	icon = 'icons/obj/containers/walllocker.dmi'
 	icon_state = "walllocker" //...man, how OLD is this $#!?
 	door_anim_angle = 132
 	door_anim_squish = 0.38

code/game/objects/structures/crates_lockers/crates.dm

@@ -5,7 +5,7 @@
 /obj/structure/closet/crate
 	name = "crate"
 	desc = "A rectangular steel crate."
-	icon = 'icons/obj/crate.dmi'
+	icon = 'icons/obj/containers/crate.dmi'
 	icon_state = "crate"
 	climbable = TRUE
 	build_amt = 10
@@ -240,7 +240,6 @@
 /obj/structure/closet/crate/secure
 	name = "secure crate"
 	desc = "A secure crate."
-	icon_state = "secure_crate"
 	locked = TRUE
 	secure = TRUE
 	secure_lights = TRUE
@@ -488,12 +487,12 @@
 /obj/structure/closet/crate/secure/weapon
 	name = "weapons crate"
 	desc = "A secure weapons crate."
-	icon_state = "syndi_secure_crate"
+	icon_state = "syndi_crate"
 	icon_door_override = TRUE
 	icon_door = "syndi_crate"
 
 /obj/structure/closet/crate/secure/weapon/alt
-	icon_state = "syndi_secure_crate1"
+	icon_state = "syndi_crate1"
 	icon_door = "syndi_crate1"
 
 /obj/structure/closet/crate/secure/legion
@@ -516,8 +515,8 @@
 
 /obj/structure/closet/crate/secure/hydrosec
 	name = "secure hydroponics crate"
-	desc = "A crate with a lock on it, painted in the scheme of the station's botanists."
-	icon_state = "hydro_secure_crate"
+	desc = "A crate painted in the scheme of the station's botanists."
+	icon_state = "hydro_crate"
 	req_one_access = list(ACCESS_HYDROPONICS, ACCESS_XENOBOTANY)
 
 /obj/structure/closet/crate/secure/bin

code/game/objects/structures/safe.dm

@@ -8,7 +8,7 @@ FLOOR SAFES
 /obj/structure/safe
 	name = "safe"
 	desc = "A huge chunk of metal with a dial embedded in it. Fine print on the dial reads \"Scarborough Arms - 2 tumbler safe, guaranteed thermite resistant, explosion resistant, and assistant resistant.\""
-	icon = 'icons/obj/safe.dmi'
+	icon = 'icons/obj/containers/safe.dmi'
 	icon_state = "safe"
 	anchored = 1
 	density = 1

code/game/objects/structures/tranqcabinet.dm

@@ -1,7 +1,7 @@
 /obj/structure/tranqcabinet
 	name = "tranquilizer rifle cabinet"
 	desc = "A wall mounted cabinet designed to hold a tranquilizer rifle."
-	icon = 'icons/obj/closet.dmi'
+	icon = 'icons/obj/containers/closet.dmi'
 	icon_state = "tranq_closed"
 	anchored = 1
 	density = 0

code/game/objects/structures/under_wardrobe.dm

@@ -1,7 +1,7 @@
 /obj/structure/undies_wardrobe
 	name = "underwear wardrobe"
 	desc = "Holds item of clothing you shouldn't be showing off in the hallways."
-	icon = 'icons/obj/closet.dmi'
+	icon = 'icons/obj/containers/closet.dmi'
 	icon_state = "cabinet"
 	density = 1