chore(template): change default package manager to uv

Set the default package manager from pixi to uv in copier configuration. This change aligns with the project's shift towards uv as the preferred Python package manager due to its performance advantages and modern toolchain integration.

Author: liblaf

copier.yaml

@@ -129,4 +129,4 @@ package_manager:
   choices:
     - pixi
     - uv
-  default: pixi
+  default: uv