Introduce bb CLI namespace

[codeforester]

Summary

• Add the side-by-side bb console command for financial intelligence v2 workflows.
• Move new v2 DAO/record helpers under the bankbuddy.bb namespace.
• Keep existing bankbuddy and taxbuddy commands intact while documenting the transition path.

Validation

• uv run pytest tests/test_bb_cli.py tests/test_bb_foundation.py tests/test_packaging.py -q
• ./tests/validate.sh
• git diff --check
• git diff --cached --check

Closes #126