Initialize Article Data Manager project

tests/unit/test_article_model.py

@@ -0,0 +1,14 @@
+import pytest
+
+from article_data_manager.models import Article
+
+
+def test_article_number_is_string_and_preserves_leading_zero() -> None:
+    article = Article(nr="000123", name="Example")
+
+    assert article.nr == "000123"
+
+
+def test_article_number_rejects_numeric_value() -> None:
+    with pytest.raises(TypeError):
+        Article(nr=123)  # type: ignore[arg-type]