build: switch to uv_build backend

Use uv's native build backend instead of hatchling for better
integration with uv tooling and improved build performance.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: JacobCoffee

pyproject.toml

@@ -42,15 +42,5 @@ Changelog = "https://github.com/JacobCoffee/bunenv/releases"
 bunenv = "bunenv:main"
 
 [build-system]
-requires = ["hatchling"]
-build-backend = "hatchling.build"
-
-[tool.hatch.build.targets.wheel]
-packages = ["src/bunenv"]
-
-[tool.hatch.build.targets.sdist]
-include = [
-    "/src",
-    "/README.md",
-    "/LICENSE",
-]
+requires = ["uv_build>=0.9.11,<0.10.0"]
+build-backend = "uv_build"