feat(plan): REST /api/tasks/planning endpoint

tests/test_routes_planning.py

@@ -0,0 +1,12 @@
+import inspect
+
+
+def test_planning_handler_callable():
+    from fabledassistant.routes import tasks as tasks_routes
+    assert callable(tasks_routes.start_planning_route)
+
+
+def test_planning_service_signature():
+    from fabledassistant.services.planning import start_planning
+    params = inspect.signature(start_planning).parameters
+    assert "user_id" in params and "project_id" in params and "title" in params