Air-gap: remove dead CDN reference + in-app /docs

- Removed a dead IE<9-only html5shim script tag pointing at a domain
  that no longer resolves.
- New GET /docs (index) and /docs/:slug routes render this project's
  own README, DEPLOYMENT, API.md, docs/*.md, and directory_spec.md
  server-side via marked -- so the documentation is readable from the
  running app with no route to GitHub Pages, where it otherwise only
  lives. Public, no auth, rate-limited (middleware/rate_limit.js) like
  the other public routes.
- .dockerignore/Dockerfile.openldap updated to copy DEPLOYMENT.md,
  API.md, directory_spec.md, and docs/ into the image, mirroring the
  existing tos.md -> /tos.md convention.

Dockerfile.openldap

@@ -95,6 +95,14 @@ COPY nodejs/public ./public
 # level above the nodejs/ app dir). Without this the app crashes on startup.
 COPY tos.md /tos.md
 
+# Documentation, served in-app at /docs (routes/docs.js) so it's readable
+# without internet access. Same flattened-path convention as tos.md above.
+COPY README.md /README.md
+COPY DEPLOYMENT.md /DEPLOYMENT.md
+COPY API.md /API.md
+COPY directory_spec.md /directory_spec.md
+COPY docs /docs
+
 # Baked commit hash from the gitinfo stage (see build_info.js).
 COPY --from=gitinfo /commit.txt ./.build_commit