add a first-class brainlayer --version flag

[EtanHey]

Problem

brainlayer --version and brainlayer -V are not available. Operators must shell out to Homebrew to determine the installed version, which is unreliable for non-Homebrew installs and awkward for health checks.

Reproduction

brainlayer --version
# Error: No such option: --version

The package already exposes brainlayer.__version__.

Expected

brainlayer --version
# brainlayer 1.5.1

Acceptance

• --version works without opening the DB or loading ML dependencies.
• Output is sourced from the installed package version.
• A short alias such as -V is supported if consistent with the CLI framework.
• Tests cover wheel/editable installs without assuming Homebrew.