Stamp the git commit into images built from the Dockerfile (closes #236)

.dockerignore left out .git, so `make build` in the image found no git
metadata and stamped `dev`. It now sends .git, and no longer leaves out
tracked files (LICENSE, README.md, ...), which git would see as deleted
and mark the version -dirty. The footer, startup log and /health already
read the same version; the README says to build from a git clone.

Model: opus-5-5

TODO.md

@@ -20,6 +20,11 @@ regress.
 
 # Completed Steps
 
+- 2026-09-29: An image built from the `Dockerfile` now shows the commit it was
+  built from (the `git describe` output) in the footer, the startup log and
+  `/health` instead of `dev`: `.dockerignore` no longer leaves out `.git`, nor
+  any tracked file, which git would count as deleted and mark `-dirty` (#236).
+
 - 2026-09-29: `docker-compose.yml` now sets `UPAAS_PORT` to 8080 as well as
   `PORT`, since upaas reads `UPAAS_PORT` first and a `UPAAS_PORT` in `.env` made
   it listen away from the port mapping and healthcheck; the README's Compose