Document the repo, and stop server/data at the gitignore

The setup notes described moving the project as a tarball and never mentioned
git, because until now there was no repo. They now lead with the clone URL and
what a push needs — the credential helper, a token, and the hostname rather
than 10.3.8.90, since the stored credential is keyed to the hostname and a
remote written against the bare IP prompts every time.

server/.gitignore only excluded data/*.json, which was enough for the checklist
file and nothing else. Running the server locally creates data/uploads, data/docs
and data/backups beside it, so an attached PDF or a backup would have been
committed on the next add. The whole directory is ignored now. That data lives
on the NAS; a stale copy of it restored over production is the accident worth
designing out.

Also records that the NAS password is a keychain item rather than a file, so a
future machine knows to store it instead of hunting for the line that used to
be in build-deploy.sh.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/.gitignore

@@ -1,4 +1,10 @@
 node_modules
 .env
-data/*.json
 *.log
+
+# The live checklists, uploads, docs and backups. These belong on the NAS, not in
+# the repo: the previous rule only caught data/*.json, so an uploaded PDF or a backup
+# would have been committed. Ignore the directory outright — a stale copy restored
+# over production is exactly the accident worth designing out.
+data/
+data-smoke/