Rebuild tank equipment plugin

[eleanor-ln]

Summary

• rewrite the plugin to provide the requested tank armor, weapon, and medkit commands without helicopter or gun logic
• apply the correct potion effects when custom armor or weapons are equipped and clean them up when removed
• implement the timed medkit countdown healing behaviour and simplify the Gradle build configuration

Testing

• ./gradlew build

---

https://chatgpt.com/codex/tasks/task_e_68fc85f51d48833280f4587f2ae308c3