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.

nodejs/views/bottom.ejs

@@ -10,6 +10,9 @@
 				<a href="https://github.com/theta42/sso-manager-node/blob/master/LICENSE" target="_blank" class="text-light">MIT License</a>
 			</span>
 			<span class="d-flex align-items-center gap-3">
+				<a href="/docs" class="text-light text-decoration-none">
+					<i class="fa-solid fa-book"></i> Docs
+				</a>
 				<a href="https://github.com/theta42/sso-manager-node" target="_blank" class="text-light text-decoration-none">
 					<i class="fa-brands fa-github"></i> GitHub
 				</a>