Carousing Skill (#22381)

We did need more minor/low consequence skills for the Everyday skills
category. This one was suggested by Taco on the discord.

<img width="1101" height="651" alt="image"
src="https://github.com/user-attachments/assets/a820abd9-de71-4bd4-a4d4-d09f6226b9db"
/>

This skill simply makes a character better at drinking booze and doing
drugs, by slightly improving their liver effectiveness. The actual
numbers are quite small, nowhere near the level a Galatean's Boosted
Liver might be.

<img width="684" height="207" alt="image"
src="https://github.com/user-attachments/assets/7672cc1d-3822-4fdf-953a-cbb411ee4371"
/>

code/datums/components/skills/service/carousing_skill_component.dm

@@ -0,0 +1,21 @@
+/datum/component/skill/carousing
+	/// The amount of bonus liver efficiency per bought rank of the Carousing skill
+	var/filter_strength_mod_per_rank = 0.05
+
+/datum/component/skill/carousing/Initialize(level)
+	. = ..()
+	if (!parent)
+		return
+
+	RegisterSignal(parent, COMSIG_LIVER_FILTER_EVENT, PROC_REF(modify_liver))
+
+/datum/component/skill/carousing/Destroy(force)
+	if (!parent)
+		return ..()
+
+	UnregisterSignal(parent, COMSIG_LIVER_FILTER_EVENT)
+	return ..()
+
+/datum/component/skill/carousing/proc/modify_liver(owner, filter_effect, filter_strength, toxin_healing_rate, canceled)
+	SIGNAL_HANDLER
+	*filter_strength = *filter_strength * (1 + (skill_level - 1) * filter_strength_mod_per_rank)