Enable and configure mypy

[paktusov]

Goal
Introduce static type checking with mypy and run it in CI and via Makefile.

Scope
Add mypy and required type stubs to dependencies.
Update pyproject.toml section.
Add mypy to make linters.
Update GitHub Actions to run mypy.

Acceptance Criteria
mypy runs locally and in CI without errors.
CI fails on new type errors.

PS: I recommend starting with finmars-workflow