Update database file path handling and server shutdown message (#1686)

* Update database file path handling in base.py and version.py

* Update server.py to handle SIGINT signal in LangflowUvicornWorker

* Add shutdown message when shutting down Langflow in main.py

* Update datetime type for created_at and updated_at fields in apikey and variable tables

* Update package versions in pyproject.toml and poetry.lock files

* Update package versions in pyproject.toml and poetry.lock files

* Fix import error in base.py

* Refactor database file path handling in base.py

* Update unit test command in python_test.yml