Switch Python build backend from setuptools to hatchling

Replace the split setuptools configuration (pyproject.toml + setup.cfg) with
a unified hatchling-based setup. This adds a [build-system] section pointing
to hatchling and a build hook (hatch_build.py) that marks wheels as
platform-specific since we bundle native shared libraries.

Hatchling includes all files in the package directory by default, which also
fixes the missing *.dll glob that setup.cfg had for Windows.

Bump requires-python from >=3.6 to >=3.8 as 3.6/3.7 are long EOL.

Co-Authored-By: HAL 9000

Author: tnull

bindings/python/hatch_build.py

@@ -0,0 +1,7 @@
+from hatchling.builders.hooks.plugin.interface import BuildHookInterface
+
+
+class CustomBuildHook(BuildHookInterface):
+    def initialize(self, version, build_data):
+        build_data["pure_python"] = False
+        build_data["infer_tag"] = True

bindings/python/pyproject.toml

@@ -1,3 +1,7 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
 [project]
 name = "ldk_node"
 version = "0.7.0"
@@ -6,7 +10,7 @@ authors = [
 ]
 description = "A ready-to-go Lightning node library built using LDK and BDK."
 readme = "README.md"
-requires-python = ">=3.6"
+requires-python = ">=3.8"
 classifiers = [
     "Topic :: Software Development :: Libraries",
     "Topic :: Security :: Cryptography",
@@ -19,3 +23,6 @@ classifiers = [
 "Homepage" = "https://lightningdevkit.org/"
 "Github" = "https://github.com/lightningdevkit/ldk-node"
 "Bug Tracker" = "https://github.com/lightningdevkit/ldk-node/issues"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/ldk_node"]