feat: integrate Atlantis Disguises API for packet-level nick/skin support

- Added net.atlantismc.disguises:api:1.0 as compileOnly dependency
- Created AtlantisDisguiseIntegration bridge class
- NameOverrideService now delegates to Atlantis when available
- Falls back to built-in Bukkit display name overrides if absent
- Added AtlantisDisguises to plugin.yml softdepend

build.gradle.kts

@@ -15,6 +15,7 @@ allprojects {
         mavenCentral()
         maven("https://repo.papermc.io/repository/maven-public/")
         maven("https://repo.extendedclip.com/releases/") // PlaceholderAPI
+        maven("https://repo.selixe.com/repository/api/") // Atlantis Disguises
     }
 }