feat(normalizer): add persons_tree skeleton + year extraction

tools/import-normalizer/tests/test_persons_tree.py

@@ -0,0 +1,54 @@
+import sys
+from pathlib import Path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+import persons_tree
+
+
+def test_parse_year_iso_string():
+    assert persons_tree._parse_year("1920-09-20") == 1920
+
+
+def test_parse_year_excel_serial_birth():
+    # 7568 days from 1899-12-30 = 1920-09-19 or -20 depending on leap counting
+    assert persons_tree._parse_year("7568") == 1920
+
+
+def test_parse_year_excel_serial_death():
+    # 36222 days from 1899-12-30 ≈ 1999
+    assert persons_tree._parse_year("36222") == 1999
+
+
+def test_parse_year_excel_serial_small():
+    # 177 days from 1899-12-30 = 1900-06-25
+    assert persons_tree._parse_year("177") == 1900
+
+
+def test_parse_year_german_date_string():
+    assert persons_tree._parse_year("30.8.1862") == 1862
+
+
+def test_parse_year_year_only():
+    assert persons_tree._parse_year("1930") == 1930
+
+
+def test_parse_year_free_text():
+    assert persons_tree._parse_year("August 1941") == 1941
+
+
+def test_parse_year_none():
+    assert persons_tree._parse_year(None) is None
+
+
+def test_parse_year_empty():
+    assert persons_tree._parse_year("") is None
+
+
+def test_parse_year_unresolvable_truncated():
+    # "2.9.196" has no valid 4-digit year — returns None
+    assert persons_tree._parse_year("2.9.196") is None
+
+
+def test_parse_year_typo_year():
+    # "4.3.1023" — year 1023 outside 1500-2100 guard — returns None
+    assert persons_tree._parse_year("4.3.1023") is None