Stop double-reporting overdue claims and add SEPA-specific followup

The claim-status and reminder-due housekeeper rules used to run
independently, so once a claim was both overdue and past its dunning
grace period, both a generic "überfällig" task and a "Mahnung fällig"
task showed up for the same problem. Rules can't see each other's
output, so the fix is to give reminder-due sole ownership of the whole
overdue lifecycle: a plain overdue notice during the grace period, then
either the dunning escalation or a fallback overdue notice (dunning
hold active, or waiting between reminder levels) -- never both at once.
claim-status now only handles claims that aren't overdue yet ("bald
fällig").

Members with an active SEPA mandate get a new sepa_debit_overdue finding
instead of the postal dunning escalation once a claim is past its grace
period, since mailing a Mahnung makes no sense for a member who pays by
direct debit -- the board needs to check/retrigger the debit instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_housekeeper.py

@@ -29,11 +29,10 @@ def test_housekeeper_reports_initial_payment_and_open_claims(tmp_path) -> None:
     )
 
     findings = Housekeeper(repository).run(today=date(2026, 2, 10))
-    assert {finding.code for finding in findings} == {
-        "initial_payment_overdue",
-        "claim_overdue",
-        "reminder_due",
-    }
+    # Both claims are more than the default 7-day grace period overdue, so the dunning
+    # escalation ("reminder_due") is the single active finding for each -- no separate,
+    # redundant "overdue" finding alongside it.
+    assert {finding.code for finding in findings} == {"reminder_due"}
 
 
 def test_housekeeper_reports_birthdays_before_today_and_after(tmp_path) -> None:

tests/test_reminders.py

@@ -68,7 +68,11 @@ def test_dunning_hold_suppresses_and_then_restores_task(tmp_path) -> None:
         reason="Betrag wird geklärt",
     )
 
-    assert not any(item.code == "reminder_due" for item in housekeeper.run(today=date(2026, 2, 10)))
+    findings = housekeeper.run(today=date(2026, 2, 10))
+    assert not any(item.code == "reminder_due" for item in findings)
+    # The claim stays visible as a plain overdue notice instead of disappearing entirely
+    # while the hold suppresses the dunning escalation.
+    assert any(item.code == "claim_overdue" for item in findings)
     with pytest.raises(RepositoryError, match="Mahnsperre aktiv"):
         repository.create_reminder_draft(
             member.member_id,
@@ -81,6 +85,41 @@ def test_dunning_hold_suppresses_and_then_restores_task(tmp_path) -> None:
     assert any(item.code == "reminder_due" for item in housekeeper.run(today=date(2026, 2, 10)))
 
 
+def test_overdue_claim_and_reminder_finding_are_never_shown_at_once(tmp_path) -> None:
+    repository, member = _overdue_claim_repository(tmp_path)
+    housekeeper = Housekeeper(repository)
+
+    # Still within the 7-day default grace period: only the plain overdue notice, no
+    # dunning escalation yet.
+    within_grace = housekeeper.run(today=date(2026, 2, 4))
+    codes = {item.code for item in within_grace if item.member_id == member.member_id}
+    assert codes == {"claim_overdue"}
+
+    # Past the grace period: the dunning escalation takes over as the single finding,
+    # the redundant plain overdue notice disappears.
+    past_grace = housekeeper.run(today=date(2026, 2, 10))
+    codes = {item.code for item in past_grace if item.member_id == member.member_id}
+    assert codes == {"reminder_due"}
+
+
+def test_sepa_member_gets_debit_followup_instead_of_reminder(tmp_path) -> None:
+    repository, member = _overdue_claim_repository(tmp_path)
+    member.iban = "DE89370400440532013000"
+    member.mandate_reference = "MANDATE-1"
+    member.mandate_signed_at = "2026-01-01"
+    member.mandate_active = True
+    repository.save_member(member)
+    housekeeper = Housekeeper(repository)
+
+    findings = housekeeper.run(today=date(2026, 2, 10))
+    codes = {item.code for item in findings if item.member_id == member.member_id}
+
+    assert codes == {"sepa_debit_overdue"}
+    sepa_finding = next(item for item in findings if item.code == "sepa_debit_overdue")
+    assert "Lastschrift" in sepa_finding.title
+    assert "SEPA" in sepa_finding.detail
+
+
 def test_draft_can_be_cancelled_but_sent_reminder_cannot(tmp_path) -> None:
     repository, member = _overdue_claim_repository(tmp_path)
     draft = repository.create_reminder_draft(