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/routes/docs.js

@@ -0,0 +1,71 @@
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const router = require('express').Router();
+const {marked} = require('marked');
+const conf = require('@simpleworkjs/conf');
+const buildInfo = require('../utils/build_info');
+const rateLimit = require('../middleware/rate_limit');
+
+const values = {
+	title: conf.environment !== 'production' ? `dev` : '',
+	titleIcon: conf.environment !== 'production' ? `<i class="fa-brands fa-dev"></i>` : '',
+	name: conf.name,
+	...buildInfo,
+};
+
+// Full local copy of the project's documentation, rendered server-side --
+// so an operator running air-gapped (no route to GitHub Pages, where this
+// content otherwise only lives) can still read it from the running app.
+// An explicit slug -> file allowlist, never a user-suppliable path, so
+// there's no way to make this read outside the doc set below.
+// docs/deployment.md is deliberately excluded -- it's just a stub pointing
+// back at the root DEPLOYMENT.md (see docs/deployment.md itself), which is
+// already covered by the "deployment" entry.
+const DOCS = {
+	overview:        {title: 'Overview',        file: path.join(__dirname, '../../README.md')},
+	deployment:      {title: 'Deployment',      file: path.join(__dirname, '../../DEPLOYMENT.md')},
+	api:             {title: 'API Reference',   file: path.join(__dirname, '../../API.md')},
+	ldap:            {title: 'LDAP',            file: path.join(__dirname, '../../docs/ldap.md')},
+	oauth:           {title: 'OAuth',           file: path.join(__dirname, '../../docs/oauth.md')},
+	configuration:   {title: 'Configuration',   file: path.join(__dirname, '../../docs/configuration.md')},
+	'directory-spec': {title: 'Directory Spec (draft)', file: path.join(__dirname, '../../directory_spec.md')},
+};
+
+const docList = Object.entries(DOCS).map(([slug, d]) => ({slug, title: d.title}));
+
+// README.md links its screenshots as repo-relative "docs/images/...", which
+// only resolves correctly on GitHub. Serve that same folder here and rewrite
+// the rendered markup to point at it absolutely, so the images work when
+// read from /docs/overview too.
+router.use('/images', require('express').static(path.join(__dirname, '../../docs/images')));
+function fixImagePaths(html) {
+	return html.replace(/(["(])docs\/images\//g, '$1/docs/images/');
+}
+
+router.use(rateLimit.docs);
+
+router.get('/', function(req, res) {
+	res.render('docs_index', {...values, docs: docList});
+});
+
+router.get('/:slug', function(req, res, next) {
+	const doc = DOCS[req.params.slug];
+	if (!doc) return next({status: 404, message: 'Doc not found'});
+
+	try {
+		const content = fs.readFileSync(doc.file, 'utf8');
+		res.render('docs_page', {
+			...values,
+			docs: docList,
+			currentSlug: req.params.slug,
+			docTitle: doc.title,
+			docHtml: fixImagePaths(marked(content)),
+		});
+	} catch (error) {
+		next(error);
+	}
+});
+
+module.exports = router;