feat: add per-member payment frequencies

tests/test_repository.py

@@ -40,9 +40,32 @@ def test_repository_creates_transparent_member_record(tmp_path) -> None:
     assert raw["person"]["nickname"] == "Enchantress"
     assert raw["schema_version"] == 1
     assert raw["membership"]["ended_at"] == ""
+    assert raw["contribution_profile"]["payment_frequency"] == "semiannual"
     assert raw["content_hash"]
 
 
+def test_existing_member_without_payment_frequency_defaults_to_semiannual(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    member = repository.create_member(first_name="Legacy", last_name="Member")
+    member_path = repository.members_root / member.member_id / "member.json"
+    raw = json.loads(member_path.read_text(encoding="utf-8"))
+    raw["contribution_profile"].pop("payment_frequency")
+    member_path.write_text(json.dumps(raw), encoding="utf-8")
+
+    assert repository.get_member(member.member_id).payment_frequency == "semiannual"
+
+
+def test_repository_rejects_unknown_payment_frequency(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    member = repository.create_member(first_name="Invalid", last_name="Frequency")
+    member.payment_frequency = "weekly"
+
+    with pytest.raises(RepositoryError, match="Ungültige Zahlweise"):
+        repository.save_member(member)
+
+
 def test_search_matches_name_email_number_and_german_birth_date(tmp_path) -> None:
     repository = MemberRepository(tmp_path)
     repository.initialize()