chore(deps): upgrade to Python 3.12 with latest dependencies

- Bump requires-python to >=3.12 and mypy python_version to 3.12 - Update all dependency minimums to latest stable releases: fastapi 0.135, uvicorn 0.42, pydantic 2.12, pydantic-settings 2.13, sqlalchemy 2.0.48, alembic 1.18, httpx 0.28, anyio 4.12, websockets 16, aiofiles 25.1, asyncpg 0.31, cryptography 46, boto3 1.42, mido 1.3.3, pyyaml 6.0.3, typer 0.24, pytest 9, pytest-asyncio 1.3, pytest-cov 7, pytest-xdist 3.8, mypy 1.19, PyJWT 2.12 - Add asyncio_default_fixture_loop_scope = "function" for pytest-asyncio 1.x - Update CI workflow to Python 3.12 - Modernize type annotations to Python 3.12 idioms: Optional[X] -> X | None, Union[X, Y] -> X | Y, Type[X] -> type[X]