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.

.dockerignore

@@ -9,9 +9,15 @@
 .claude
 *.md
 # README.md and tos.md are both read at runtime (tos.md is loaded by
-# routes/index.js at boot), so they must stay in the build context.
+# routes/index.js at boot). DEPLOYMENT.md/API.md/directory_spec.md/docs/*.md
+# are read at runtime too, by routes/docs.js -- all must stay in the build
+# context.
 !README.md
 !tos.md
+!DEPLOYMENT.md
+!API.md
+!directory_spec.md
+!docs/**/*.md
 
 # Tests
 nodejs/tests/