Initialize Article Data Manager project

tests/unit/test_article_number.py

@@ -0,0 +1,12 @@
+import pytest
+
+from article_data_manager.validation import normalize_article_number
+
+
+def test_normalize_article_number_trims_but_preserves_leading_zero() -> None:
+    assert normalize_article_number(" 000123 ") == "000123"
+
+
+def test_normalize_article_number_rejects_non_string() -> None:
+    with pytest.raises(TypeError):
+        normalize_article_number(123)  # type: ignore[arg-type]