feat: Start/Ende fuer Fixposten in der GUI + Datumsvalidierung

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

finance/tests/test_gui.py

@@ -225,6 +225,18 @@ def test_planning_page_has_all_sections(client):
         assert heading in r.text
 
 
+def test_planung_fixposten_zeigt_start_und_ende(client, db):
+    client.post("/login", data={"username": "admin", "password": "geheim"})
+    db.add(RecurringItem(name="Befristet-GUI", amount=Decimal("-5.00"),
+                         rhythm="monthly", due_day=1,
+                         start_date=date(2026, 1, 1), end_date=date(2026, 12, 31)))
+    db.commit()
+    r = client.get("/planung").text
+    assert "<th>Start</th>" in r and "<th>Ende</th>" in r
+    assert "01.01.2026" in r and "31.12.2026" in r
+    assert 'name="start_date"' in r and 'name="end_date"' in r
+
+
 def test_planning_page_shows_empty_suggestions_hint(client):
     # UX-Regel: das "Vorschläge aus Buchungen"-Fieldset ist immer sichtbar,
     # auch ohne Daten - statt komplett zu verschwinden zeigt es einen Hinweis.

finance/tests/test_planning_api.py

@@ -87,6 +87,30 @@ def test_suggest_recurring_two_months_no_suggestion(db):
     assert suggest_recurring(db) == []
 
 
+def test_recurring_ende_vor_start_wird_abgelehnt(client):
+    r = client.post("/api/recurring", headers=H, json={
+        "name": "Falschrum", "amount": "-10.00", "rhythm": "monthly", "due_day": 1,
+        "start_date": "2026-10-01", "end_date": "2026-09-01"})
+    assert r.status_code == 422
+
+
+def test_recurring_start_ende_roundtrip_und_patch_validierung(client):
+    r = client.post("/api/recurring", headers=H, json={
+        "name": "Befristet", "amount": "-10.00", "rhythm": "monthly", "due_day": 1,
+        "start_date": "2026-01-01", "end_date": "2026-12-31"})
+    assert r.status_code == 201
+    item = r.json()
+    assert item["start_date"] == "2026-01-01" and item["end_date"] == "2026-12-31"
+    # PATCH, der Ende vor den (bestehenden) Start schieben will -> 422:
+    bad = client.patch(f"/api/recurring/{item['id']}", headers=H,
+                       json={"end_date": "2025-06-30"})
+    assert bad.status_code == 422
+    # Datum explizit loeschen (null) ist erlaubt:
+    ok = client.patch(f"/api/recurring/{item['id']}", headers=H,
+                      json={"end_date": None})
+    assert ok.status_code == 200 and ok.json()["end_date"] is None
+
+
 def test_suggest_recurring_excludes_existing_recurring_item(db):
     acc = Account(bank="dkb", iban="DE01", name="G", type="giro")
     db.add(acc)