[DOP-16658] Initialize repo

[dolfinus]

Copy base repo structure from Horizon with following changes:

• Remove all business logic, DB models & migrations, API routes & schemas.
• Remove client.
• Remove related tests.
• Remove CI/CD related to publishing artifacts like PyPI packages and Docker images, for now.
• Bump minimal Python version to 3.10 (we need match syntax).
• Cleanup dependencies list.

pre-commit.ci and CodeQL integrations are disabled for now, as requiring paid plan on private repos.

[codecov]

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