Stop tracking macOS .DS_Store files

Finder metadata was tracked at the repository root and nearly got
packaged inside the integration. Ignore .DS_Store everywhere, untrack
the root copy (the local file stays) and make the package check reject
it under custom_components.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -4,3 +4,4 @@ __pycache__/
 .coverage
 htmlcov/
 .venv/
+.DS_Store

scripts/validate_package.py

@@ -36,5 +36,5 @@ for name, size in (("icon.png", 256), ("icon@2x.png", 512),
     assert (width, height) == (size, size), f"{name} is {width}x{height}, expected {size}x{size}"
     assert color_type == 6, f"{name} needs an alpha channel"
 tracked = subprocess.check_output(["git", "ls-files", "custom_components"], cwd=root, text=True).splitlines()
-assert not any("__pycache__" in path or path.endswith((".pyc", ".pyo")) for path in tracked)
+assert not any("__pycache__" in path or path.endswith((".pyc", ".pyo", ".DS_Store")) for path in tracked)
 print("Package metadata, translations, brand icons and tracked component files passed")