refactor(npc): move heal helper to shared npclib

Move registerHealKeyword from the global datapack functions into the shared NPC custom modules loaded by npclib, so NPC scripts from either supported datapack can reuse it. Remove the datapack-specific load entry and delete the obsolete helper file without changing the existing NPC call sites or healing behavior.

Validation: confirmed 83 NPC helper calls and one shared definition, confirmed no addHealKeyword pattern remains, checked staged Lua syntax and StyLua for the relocated library and load file, ran the staged whitespace check, and exercised the helper behavior from the staged shared module.

Author: dudantas

data-otservbr-global/lib/functions/load.lua

@@ -1,2 +1 @@
 dofile(DATA_DIRECTORY .. "/lib/functions/players.lua")
-dofile(DATA_DIRECTORY .. "/lib/functions/npcs.lua")

data-otservbr-global/lib/functions/npcs.lua

@@ -1,4 +1,20 @@
--- Custom Modules, created to help us in this datapack
+-- Custom modules used by the NPC system
+function registerHealKeyword(keywordHandler, npcHandler, text, condition, effect, minimumHealth)
+	keywordHandler:addKeyword({ "heal" }, StdModule.say, { npcHandler = npcHandler, text = text }, function(player)
+		return player:getCondition(condition) ~= nil
+	end, function(player)
+		if minimumHealth then
+			local health = player:getHealth()
+			if health < minimumHealth then
+				player:addHealth(minimumHealth - health)
+			end
+		end
+
+		player:removeCondition(condition)
+		player:getPosition():sendMagicEffect(effect)
+	end)
+end
+
 local travelDiscounts = {
 	["postman"] = { price = 10, storage = Storage.Quest.ExampleQuest, value = 1 },
 }