feat: support custom task recurrence

tests/test_mvp_backend.py

@@ -29,6 +29,22 @@ def test_bootstrap_returns_navigation_and_current_user(client):
 
 
 
+def test_custom_recurrence_rejects_invalid_weekdays_month_days_and_until(client):
+    inbox = boot(client)
+    task = client.post(
+        "/api/v1/tasks",
+        json={"title": "自定义重复", "list_id": inbox["id"], "due_at": "2026-09-07T09:00:00Z"},
+    ).json()
+    for rrule in (
+        "FREQ=WEEKLY;BYDAY=XX",
+        "FREQ=MONTHLY;BYMONTHDAY=0,32",
+        "FREQ=DAILY;UNTIL=not-a-date",
+        "FREQ=DAILY;UNKNOWN=1",
+    ):
+        response = client.post("/api/v1/recurrences", json={"task_id": task["id"], "rrule": rrule})
+        assert response.status_code == 422
+
+
 def test_get_recurrence_by_task_returns_rule_or_null(client):
     inbox = boot(client)
     task = client.post(