BIRP to URP

This one was a damn pain. Antorum has been running on Unity's built-in render pipeline (BIRP) for most of its life. BIRP is the old default, the one that shipped with Unity for over a decade. It's battle-tested and honestly looks fine, but it's showing its age, and Unity is actually going to deprecate it soon . Since I'm already on the latest Unity version, it felt like the right time to drag…