feat(v4.4.0): Tasks, Sub-items & Dependencies

- Add is_task flag on collections (toggle-task API)
- New page_dependencies table with auto_shift config (blocks/blocked_by/related)
- API: GET/POST/DELETE page dependencies
- API: POST auto-shift dates based on blocking dependencies (skip_weekends option)
- 5 new tests (171 total)

tests/test_app.py

@@ -2451,4 +2451,121 @@ def test_view_unknown_falls_back_to_table(client):
     coll_id = resp.json()["id"]
     resp = client.get(f"/db/{coll_id}/view/unknown_view_type")
     assert resp.status_code == 200
-    assert "<table>" in resp.text
+    assert "<table>" in resp.text
+
+
+# ── v4.4.0: Tasks & Dependencies ──
+
+
+def test_toggle_task_flag(client):
+    """Toggle is_task on a collection."""
+    resp = client.post("/db/api", json={"name": "Task DB"})
+    coll_id = resp.json()["id"]
+
+    resp = client.put(f"/db/{coll_id}/toggle-task/api")
+    assert resp.status_code == 200
+    assert resp.json()["is_task"] is True
+    assert resp.json()["mode"] == "tasks"
+
+    resp = client.get(f"/db/{coll_id}/api")
+    assert resp.json()["collection"]["is_task"] == 1
+
+    # Toggle back
+    resp = client.put(f"/db/{coll_id}/toggle-task/api")
+    assert resp.json()["is_task"] is False
+    assert resp.json()["mode"] == "standard"
+
+
+def test_page_dependencies_crud(client):
+    """Add, list, and remove page dependencies."""
+    resp = client.post("/db/api", json={"name": "Dep DB"})
+    coll_id = resp.json()["id"]
+
+    p1 = client.post(f"/db/{coll_id}/pages/api", json={"title": "Task A"})
+    p2 = client.post(f"/db/{coll_id}/pages/api", json={"title": "Task B"})
+    pid1 = p1.json()["id"]
+    pid2 = p2.json()["id"]
+
+    # Add dependency: Task A blocks Task B
+    resp = client.post(f"/db/{coll_id}/pages/{pid2}/dependencies/api", json={
+        "dependency_id": pid1,
+        "dependency_type": "blocks",
+        "auto_shift": "overlap",
+    })
+    assert resp.status_code == 200
+    assert resp.json()["status"] == "added"
+    dep_id = resp.json()["id"]
+
+    # List dependencies
+    resp = client.get(f"/db/{coll_id}/pages/{pid2}/dependencies/api")
+    deps = resp.json()["dependencies"]
+    assert len(deps) == 1
+    assert deps[0]["dependency_type"] == "blocks"
+    assert deps[0]["dependency_title"] == "Task A"
+
+    # Remove dependency
+    resp = client.delete(f"/db/{coll_id}/pages/{pid2}/dependencies/{dep_id}/api")
+    assert resp.status_code == 200
+    assert resp.json()["status"] == "removed"
+
+    resp = client.get(f"/db/{coll_id}/pages/{pid2}/dependencies/api")
+    assert len(resp.json()["dependencies"]) == 0
+
+
+def test_page_dependencies_duplicate_rejected(client):
+    """Duplicate dependency returns 409."""
+    resp = client.post("/db/api", json={"name": "Dup Dep DB"})
+    coll_id = resp.json()["id"]
+    p1 = client.post(f"/db/{coll_id}/pages/api", json={"title": "A"})
+    p2 = client.post(f"/db/{coll_id}/pages/api", json={"title": "B"})
+
+    client.post(f"/db/{coll_id}/pages/{p2.json()['id']}/dependencies/api", json={
+        "dependency_id": p1.json()["id"],
+    })
+    resp = client.post(f"/db/{coll_id}/pages/{p2.json()['id']}/dependencies/api", json={
+        "dependency_id": p1.json()["id"],
+    })
+    assert resp.status_code == 409
+
+
+def test_auto_shift_dates(client):
+    """Auto-shift dates when a blocking task is completed."""
+    resp = client.post("/db/api", json={"name": "Shift DB"})
+    coll_id = resp.json()["id"]
+
+    # Blocking task with end date July 10
+    p1 = client.post(f"/db/{coll_id}/pages/api", json={
+        "title": "Blocker",
+        "properties": {"Timeline": "2026-07-01...2026-07-10"},
+    })
+    # Blocked task
+    p2 = client.post(f"/db/{coll_id}/pages/api", json={
+        "title": "Dependent",
+        "properties": {"Timeline": "2026-07-11...2026-07-20"},
+    })
+
+    # Add dependency
+    client.post(f"/db/{coll_id}/pages/{p2.json()['id']}/dependencies/api", json={
+        "dependency_id": p1.json()["id"],
+        "dependency_type": "blocks",
+    })
+
+    # Auto-shift
+    resp = client.post(f"/db/{coll_id}/pages/{p2.json()['id']}/auto-shift/api", json={
+        "skip_weekends": False,
+    })
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["shifted"] is True
+    assert data["new_start"] == "2026-07-11"  # day after blocker ends
+
+
+def test_auto_shift_no_blockers(client):
+    """Auto-shift with no blocking dependencies returns shifted=False."""
+    resp = client.post("/db/api", json={"name": "NoBlock DB"})
+    coll_id = resp.json()["id"]
+    p = client.post(f"/db/{coll_id}/pages/api", json={"title": "Lone Task"})
+
+    resp = client.post(f"/db/{coll_id}/pages/{p.json()['id']}/auto-shift/api")
+    assert resp.status_code == 200
+    assert resp.json()["shifted"] is False