Fix mousetrap beaker assemblies not activating when container is opened (#96783)

## About The Pull Request

Beaker needs to pass `on_found` down to the assembly

## Why It's Good For The Game

Fixes #95826 

## Changelog
🆑
fix: fixed mousetrap beaker assemblies not triggering when container is
opened
/🆑

code/modules/reagents/reagent_containers/cups/_cup.dm

@@ -355,6 +355,10 @@
 	update_appearance()
 	return TRUE
 
+/obj/item/reagent_containers/cup/on_found(mob/finder)
+	. = ..()
+	lid_assembly?.on_found(finder)
+
 /obj/item/reagent_containers/cup/Exited(atom/movable/gone, direction)
 	. = ..()
 	if (gone == lid_assembly)