feat: allow optional database configuration

[vumichien]

This PR solved #562

[badmonster0]

Thanks for this high quality PR, especially for adding additional tests carefully!

[vumichien]

@badmonster0 I'm unsure why the CI failed to create a .venv. Could you help me in rerunning the CI if necessary?. It works now after pushing some commits that altered the environment in the GitHub workflow. This is not a permanent solution; we should address the root cause in a different pull request.

[lemorage]

@vumichien personally, I think this might be due to the python version changes (?). I found the latest successful action in #611, it used Python 3.13.3 (/opt/hostedtoolcache/Python/3.13.3/x64). However, the failed ones are using Python 3.13.4 shown in the Setup venv log (/opt/hostedtoolcache/Python/3.13.4/x64).

[badmonster0]

@vumichien @lemorage Thanks for debugging! This is because the symbolic .venv/bin/python in the cache is broken when a different Python version is live. #615 should solve the problem.