feat: add permission handling for pushback inventory items

- Introduced `permission` property to `PushbackEnableInventoryItem` and `PushbackDisableInventoryItem`.
- Linked permissions to `PermissionRegistry.PUSHBACK_ITEM`.

Author: TheBjoRedCraft

src/main/kotlin/dev/slne/surf/lobby/inventory/item/impl/PushbackDisableInventoryItem.kt

@@ -2,6 +2,7 @@ package dev.slne.surf.lobby.inventory.item.impl
 
 import dev.slne.surf.lobby.inventory.item.InventoryItem
 import dev.slne.surf.lobby.manager.PushbackManager
+import dev.slne.surf.lobby.utils.PermissionRegistry
 import dev.slne.surf.surfapi.bukkit.api.builder.buildLore
 import dev.slne.surf.surfapi.bukkit.api.builder.displayName
 import org.bukkit.entity.Player
@@ -25,6 +26,7 @@ object PushbackDisableInventoryItem : InventoryItem {
             }
         }
     }
+    override val permission: String = PermissionRegistry.PUSHBACK_ITEM
 
     override fun onInteract(player: Player) {
         PushbackManager.remove(player.uniqueId)

src/main/kotlin/dev/slne/surf/lobby/inventory/item/impl/PushbackEnableInventoryItem.kt

@@ -2,13 +2,15 @@ package dev.slne.surf.lobby.inventory.item.impl
 
 import dev.slne.surf.lobby.inventory.item.InventoryItem
 import dev.slne.surf.lobby.manager.PushbackManager
+import dev.slne.surf.lobby.utils.PermissionRegistry
 import dev.slne.surf.surfapi.bukkit.api.builder.buildLore
 import dev.slne.surf.surfapi.bukkit.api.builder.displayName
 import org.bukkit.entity.Player
 import org.bukkit.inventory.ItemType
 
 object PushbackEnableInventoryItem : InventoryItem {
     override val slot = 3
+    override val permission: String = PermissionRegistry.PUSHBACK_ITEM
     override val item = ItemType.ENDER_EYE.createItemStack().apply {
         displayName {
             variableValue("Pushback")