Some wall mount improvements (#94499)

## About The Pull Request
- Fixes #94497. Adds atom mount component directly but only for non
shuttle areas
- Hand placed posters are pixel shifted onto the wall and not directly
force moved allowing for stuff like acid/fire to interact with them
- Hand placing posters & signs apply the atom mounted component directly
without calling `find_and_mount_on_atom()`

## Changelog
🆑
code: improves code for placing posters and signs on walls
fix: hand placed posters now interact with fire/acid on their mounted
turf
fix: wallframes in player hands gets consumed when mounted in shuttle
areas
/🆑

code/game/objects/structures/signs/_signs.dm

@@ -207,7 +207,7 @@
 	playsound(target_turf, 'sound/items/deconstruct.ogg', 50, TRUE)
 	placed_sign.update_integrity(get_integrity())
 	placed_sign.setDir(dir)
-	placed_sign.find_and_mount_on_atom()
+	placed_sign.AddComponent(/datum/component/atom_mounted, target_turf)
 	qdel(src)
 	return ITEM_INTERACT_SUCCESS