feat: add repeating tasks

tests/test_mvp_backend.py

@@ -29,6 +29,60 @@ def test_bootstrap_returns_navigation_and_current_user(client):
 
 
 
+def test_get_recurrence_by_task_returns_rule_or_null(client):
+    inbox = boot(client)
+    task = client.post(
+        "/api/v1/tasks",
+        json={"title": "每天复盘", "list_id": inbox["id"], "due_at": "2026-09-07T09:00:00Z"},
+    ).json()
+    empty = client.get(f"/api/v1/tasks/{task['id']}/recurrence")
+    assert empty.status_code == 200
+    assert empty.json() is None
+
+    created = client.post(
+        "/api/v1/recurrences", json={"task_id": task["id"], "rrule": "FREQ=DAILY"}
+    ).json()
+    found = client.get(f"/api/v1/tasks/{task['id']}/recurrence")
+    assert found.status_code == 200
+    assert found.json()["id"] == created["id"]
+    assert found.json()["rrule"] == "FREQ=DAILY"
+
+
+def test_export_and_restore_preserve_task_recurrence(client):
+    inbox = boot(client)
+    task = client.post(
+        "/api/v1/tasks",
+        json={"title": "每周整理", "list_id": inbox["id"], "due_at": "2026-09-07T09:00:00Z"},
+    ).json()
+    client.post("/api/v1/recurrences", json={"task_id": task["id"], "rrule": "FREQ=WEEKLY"})
+    exported = client.get("/api/v1/export").json()
+    assert exported["recurrences"][0]["task_id"] == task["id"]
+
+    restored = client.post("/api/v1/restore?mode=replace", json=exported)
+    assert restored.status_code == 200
+    restored_task = client.get("/api/v1/tasks", params={"q": "每周整理"}).json()["items"][0]
+    recurrence = client.get(f"/api/v1/tasks/{restored_task['id']}/recurrence").json()
+    assert recurrence["rrule"] == "FREQ=WEEKLY"
+
+
+def test_completing_repeating_task_advances_due_date_instead_of_closing_it(client):
+    inbox = boot(client)
+    task = client.post(
+        "/api/v1/tasks",
+        json={"title": "每日复盘", "list_id": inbox["id"], "due_at": "2026-09-07T09:00:00Z"},
+    ).json()
+    client.post("/api/v1/recurrences", json={"task_id": task["id"], "rrule": "FREQ=DAILY"})
+
+    completed = client.patch(
+        f"/api/v1/tasks/{task['id']}", json={"completed": True, "version": task["version"]}
+    )
+    assert completed.status_code == 200
+    assert completed.json()["completed"] is False
+    assert completed.json()["due_at"].replace("Z", "") == "2026-09-08T09:00:00"
+    recurrence = client.get(f"/api/v1/tasks/{task['id']}/recurrence").json()
+    assert recurrence["starts_at"].replace("Z", "") == "2026-09-08T09:00:00"
+
+
 def test_recurrence_mutations_keep_exact_timestamp_validation(client):
     inbox = boot(client)
     task = client.post(