IV Stand Click Fix (#21351)

oh wow it's me Mneme. I don't know what changed but there's a new bug
and or intended feature that's making it extremely hard to run the
GTR/throwing off everyone's flow in high intensity situations because
certain IV Stand clicks no longer register when there's a patient
buckled between them. This makes it so that isn't an issue anymore.

i.e. the IV in the solid red square would be inaccessible pre-this
change, even though prior to a couple weeks ago it was accessible. Now,
all IVs are accessible even if there's a patient buckled.
<img width="274" height="192" alt="image"
src="https://github.com/user-attachments/assets/176c44f8-7c30-4646-8775-ef49da5b0f2d"
/>

code/game/machinery/iv_drip.dm

@@ -5,7 +5,7 @@
 	icon_state = "iv_stand"
 	anchored = 0
 	density = FALSE
-	pass_flags_self = PASSTABLE
+	pass_flags_self = PASSTABLE | LETPASSCLICKS
 	var/tipped = FALSE
 	var/last_full // Spam check
 	var/last_warning