Bakes the git short commit hash into the client bundle at build time and
exposes the same info from the server via GET /api/version. The header
displays the loaded build's commit and flags when it no longer matches
what the server is running, so a stale open tab is easy to spot after a
deploy. The Docker build now includes .git so the hash can be resolved
during the image build.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
