Adds a new Odyssey map: Decrepit Shipyard (#21500)

## About PR

Adds an industrial themed away site for Odyssey scenarios. The map
starts with a shuttle, broken by a randomized destruction feature.
Actors or the crew may choose to repair it to make it fly once more

### Detailed Changelog
<details><summary>Details</summary>
<p>

- Added a new map_effect, randomized destruction. It comes with two
varieties and different impact ranges. The way it work is the effect
chooses a random amount of turfs in the area it's placed on, and calls
`ex_act` on applicable contents in the turf.
- Added unused sprites for low railing and documented relevant functions
in the existing code.
- Made it so when a railing has an open end that doesn't connect to
anywhere, it'll apply an end cap, making it look more smooth.
- Added ceiling lattices.
- Adjusted unit tests to avoid conflicts that may occur with ceiling
lattices.
- Fixed a bug where the Odyssey subsystem repeatedly added lastly loaded
z-level to the scenario z-levels, instead of all relevant levels to the
site. This was causing issues in Odyssey maps with shuttles.
- Fixed hydrogen tank not using its sprite. Also recoloured the tank to
match modern hydrogen canister colour.
- Fixed `/obj/machinery/door/airlock/maintenance` not using its intended
appearance.

</p>
</details> 

## Images

<img width="4128" height="2528" alt="StrongDMM-2025-11-10 21 33 47"
src="https://github.com/user-attachments/assets/09d8b671-457c-4ec5-88ac-e503641a0531"
/>
<img width="3424" height="2016" alt="StrongDMM-2025-11-10 21 34 27"
src="https://github.com/user-attachments/assets/943b8529-7f2a-41db-a7be-e57d5d30ead7"
/>
<img width="1312" height="800" alt="StrongDMM-2025-11-10 21 34 52"
src="https://github.com/user-attachments/assets/f665800a-367b-466e-a16e-a6f0b122e3bd"
/>
<img width="997" height="999" alt="Screenshot_54"
src="https://github.com/user-attachments/assets/c06667c6-0dfc-4dc4-af67-821f36ad2933"
/>
<img width="997" height="1001" alt="Screenshot_55"
src="https://github.com/user-attachments/assets/848a2847-9eb0-450a-87e9-08c371aaf78a"
/>
<img width="998" height="992" alt="Screenshot_61"
src="https://github.com/user-attachments/assets/e6174cb5-d4d6-4afc-82ab-bbf412eda607"
/>
<img width="998" height="990" alt="Screenshot_63"
src="https://github.com/user-attachments/assets/cc838bdc-9e22-4aed-ad16-0f8722442b8a"
/>

code/game/objects/structures/railing.dm

@@ -64,6 +64,9 @@
 	. = ..()
 	update_icon()
 
+/obj/structure/railing/mapped/no_density/low
+	icon_state = "railing0-0"
+
 /obj/structure/railing/New(var/newloc, var/material_key = DEFAULT_WALL_MATERIAL)
 	material = material_key // Converted to datum in initialize().
 	..(newloc)
@@ -136,31 +139,31 @@
 
 	for(var/obj/structure/railing/R in get_turf(src))
 		if((R.dir == Lturn) && R.anchored)
-			neighbor_status |= 32
+			neighbor_status |= 32 // neighbor is making a left turn on the same tile
 			if(UpdateNeighbors)
 				R.update_icon(0)
 		if((R.dir == Rturn) && R.anchored)
-			neighbor_status |= 2
+			neighbor_status |= 2 // neighbor is making a right turn on the same tile
 			if(UpdateNeighbors)
 				R.update_icon(0)
 	for(var/obj/structure/railing/R in get_step(src, Lturn))
 		if((R.dir == src.dir) && R.anchored)
-			neighbor_status |= 16
+			neighbor_status |= 16 // neighbor is in our left, in the same line
 			if(UpdateNeighbors)
 				R.update_icon(0)
 	for(var/obj/structure/railing/R in get_step(src, Rturn))
 		if((R.dir == src.dir) && R.anchored)
-			neighbor_status |= 1
+			neighbor_status |= 1 // neighbor is in our right, in the same line
 			if (UpdateNeighbors)
 				R.update_icon(0)
 	for(var/obj/structure/railing/R in get_step(src, (Lturn + src.dir)))
 		if((R.dir == Rturn) && R.anchored)
-			neighbor_status |= 64
+			neighbor_status |= 64 // neighbor is in our diagonal left, making a longer turn
 			if (UpdateNeighbors)
 				R.update_icon(0)
 	for(var/obj/structure/railing/R in get_step(src, (Rturn + src.dir)))
 		if((R.dir == Lturn) && R.anchored)
-			neighbor_status |= 4
+			neighbor_status |= 4 // neighbor is in our diagonal right, making a longer turn
 			if (UpdateNeighbors)
 				R.update_icon(0)
 
@@ -177,8 +180,10 @@
 		icon_state = "railing1-[density]"
 		if(neighbor_status & 32)
 			AddOverlays(image(icon, "corneroverlay[density]"))
+
 		if((neighbor_status & 16) || !(neighbor_status & 32) || (neighbor_status & 64))
 			AddOverlays(image(icon, "frontoverlay_l[density]"))
+
 		if(!(neighbor_status & 2) || (neighbor_status & 1) || (neighbor_status & 4))
 			AddOverlays(image(icon, "frontoverlay_r[density]"))
 			if(neighbor_status & 4)
@@ -195,6 +200,12 @@
 						pix_offset_y = 32
 				AddOverlays(image(icon, "mcorneroverlay[density]", pixel_x = pix_offset_x, pixel_y = pix_offset_y))
 
+		if(!(neighbor_status & 16) && !(neighbor_status & 64) && !(neighbor_status & 32)) // Left endcap, we have no connections in left
+			AddOverlays(image(icon, "frontend_l[density]"))
+
+		if(!(neighbor_status & 1) && !(neighbor_status & 4) && !(neighbor_status & 2)) // Right endcap, we have no connections in right
+			AddOverlays(image(icon, "frontend_r[density]"))
+
 /obj/structure/railing/verb/flip() // This will help push railing to remote places, such as open space turfs
 	set name = "Flip Railing"
 	set category = "Object"