Flask API for database access

[ff-dh]

Closes #11. Provides (currently unauthenticated) API access to the database on the local machine.

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Pull request checklist

• [x] I have linked my PR to an issue
• [ ] I’ve used conventional commits
• [x] My branch is up-to-date with main
• [x] Where appropriate, I have added or updated tests
• [x] Where appropriate, I have updated documentation to reflect my changes

[ff-dh]

Do you think this file is fine where it is @dcorney or should it be somewhere else in project?

[andylolz]

Is the plan to close this PR in favour of #28?