fix: avoid unnecessary database operations for non-server cli commands

[tevino]

Avoid unnecessary database operations while running non-server commands like letta version, letta benchmark, etc.

letta version has been fixed as well, it prints out Creating engine and no version before this PR.

How to test

A test case has been added to ensure that letta version prints out version number and nothing else.

For manual validation run:

• letta version should show prints out the version
• poetry run pytest -v tests/test_cli.py -k test_letta_version_prints_only_version should pass
• and definitely all other existing tests

Have you tested this PR?

root@42a43c02:/app# poetry run pytest -v tests/test_cli.py -k test_letta_version_prints_only_version
=========================================================================================================================================================================== test session starts ============================================================================================================================================================================
platform linux -- Python 3.11.2, pytest-8.3.4, pluggy-1.5.0 -- /app/.venv/bin/python
cachedir: .pytest_cache
rootdir: /app/tests
configfile: pytest.ini
plugins: asyncio-0.23.8, anyio-4.8.0, order-1.3.0, mock-3.14.0, langsmith-0.3.1
asyncio: mode=Mode.AUTO
collected 2 items / 1 deselected / 1 selected

tests/test_cli.py::test_letta_version_prints_only_version PASSED