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 and /health already read the
same version. The startup log line that reports it, the logger's
Identify(), was never called; main now calls it. The README says to
build from a git clone.

Model: opus-5-5

.dockerignore

@@ -1,11 +1,8 @@
-.git
+# .git is sent so that `make build` in the Dockerfile can stamp the commit into
+# upaas. List no tracked file here: git would see it as deleted in the build and
+# the version would end in -dirty.
 .env
 bin/
-.editorconfig
 .vscode/
 .idea/
 *.test
-LICENSE
-CONVENTIONS.md
-REPO_POLICIES.md
-README.md