Adds Blueprints to Overmap Sites (#18991)

Adds blueprints to most ships, as well as several away sites and ruins.
The only ships not to get blueprints were ones that still don't have
proper power/atmospherics setups as new areas created by blueprints will
be unpowered.

code/modules/mining/mine_turfs.dm

@@ -31,6 +31,7 @@ var/list/mineral_can_smooth_with = list(
 
 	// canSmoothWith is set in Initialize().
 	smoothing_flags = SMOOTH_MORE | SMOOTH_BORDER | SMOOTH_NO_CLEAR_ICON
+	turf_flags = TURF_FLAG_BACKGROUND
 
 	initial_gas = null
 	opacity = TRUE