refactor: convert to src-layout for Python packaging

Rename python/ to src/ following PEP 517/518 modern packaging
conventions. Also adds .gitignore for docs and build artifacts.

.gitignore

@@ -0,0 +1,4 @@
+docs-site/
+docs/
+uv.lock
+.venv/

pyproject.toml

@@ -6,14 +6,13 @@ readme = "README.md"
 license = "MIT"
 requires-python = ">=3.10"
 authors = [
-    {name = "zleffke", email = ""},
+    {name = "zleffke"},
     {name = "Ryan Malloy", email = "ryan@supported.systems"},
 ]
 keywords = ["gnuradio", "sdr", "sarsat", "cospas", "beacon", "search-rescue"]
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
     "Topic :: Communications :: Ham Radio",
 ]
@@ -31,4 +30,8 @@ requires = ["setuptools>=61.0"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools.packages.find]
-where = ["python"]
+where = ["src"]
+
+[tool.setuptools]
+# Exclude non-package directories from sdist
+exclude-package-data = {"*" = ["docs-site/**", "docs/**"]}