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

nickcore-paper/build.gradle.kts

@@ -16,6 +16,7 @@ dependencies {
 
     compileOnly("net.luckperms:api:$luckpermsVersion")
     compileOnly("me.clip:placeholderapi:$placeholderApiVersion")
+    compileOnly("net.atlantismc.disguises:api:1.0")
 }
 
 tasks.jar {