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/docs_page.ejs

@@ -0,0 +1,29 @@
+<%- include('top') %>
+<div class="row">
+	<div class="col-md-3 d-none d-md-block">
+		<div class="card shadow-lg mt-4 mb-4">
+			<div class="card-header shadow">
+				<i class="fa-solid fa-book"></i> Documentation
+			</div>
+			<div class="list-group list-group-flush">
+				<% docs.forEach(function(doc){ %>
+					<a href="/docs/<%= doc.slug %>"
+						class="list-group-item list-group-item-action<%= doc.slug === currentSlug ? ' active' : '' %>">
+						<%= doc.title %>
+					</a>
+				<% }) %>
+			</div>
+		</div>
+	</div>
+	<div class="col-md-9">
+		<div class="card shadow-lg mt-4 mb-4">
+			<div class="card-header shadow">
+				<i class="fa-solid fa-file-lines"></i> <%= docTitle %>
+			</div>
+			<div class="card-body">
+				<%- docHtml %>
+			</div>
+		</div>
+	</div>
+</div>
+<%- include('bottom') %>