feat: add custom task recurrence options

tests/test_mvp_backend.py

@@ -29,6 +29,29 @@ def test_bootstrap_returns_navigation_and_current_user(client):
 
 
 
+def test_creating_task_with_recurrence_is_atomic(client):
+    inbox = boot(client)
+    created = client.post(
+        "/api/v1/tasks",
+        json={
+            "title": "隔周复盘",
+            "list_id": inbox["id"],
+            "due_at": "2026-09-07T09:00:00Z",
+            "rrule": "FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR",
+        },
+    )
+    assert created.status_code == 201
+    recurrence = client.get(f"/api/v1/tasks/{created.json()['id']}/recurrence").json()
+    assert recurrence["rrule"] == "FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR"
+
+    rejected = client.post(
+        "/api/v1/tasks",
+        json={"title": "缺少日期", "list_id": inbox["id"], "rrule": "FREQ=DAILY"},
+    )
+    assert rejected.status_code == 422
+    assert client.get("/api/v1/tasks", params={"q": "缺少日期"}).json()["items"] == []
+
+
 def test_custom_recurrence_rejects_invalid_weekdays_month_days_and_until(client):
     inbox = boot(client)
     task = client.post(