Add plain-language concept docs; fix docs viewer rendering; link API tokens

- New docs/concepts-{accounts,oauth-apps,api-tokens}.md -- plain-language
  guides aimed at less technical readers, each linking onward to the
  existing schema/protocol-level doc for anyone who wants that detail.
  Card help links (Users, Groups, OAuth cards, My groups, Members of
  <uid>'s group) now point here instead of straight at the technical
  docs; the LDAP-protocol-wiring cards (raw connection details for
  connecting a 3rd-party app) stay pointed at the technical ldap.md,
  since that's genuinely the right depth for that task.
- The "New API Token" card had no help link at all -- added, pointing to
  the new API Tokens doc.
- Fixed the in-app docs viewer rendering every docs/*.md page with a
  garbled heading + stray <hr> at the top: Jekyll front matter (meant
  only for the GitHub Pages build) was never stripped before being
  handed to the markdown renderer. Also fixed: cross-doc links
  (ldap.html, index.html, etc.) never resolved in-app, since this
  viewer serves docs at /docs/<slug> with no .html suffix -- rewritten
  to the correct in-app URL, same idea as the existing image-path fix.

Bumps to v1.1.12.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KDEx8ghuZR61pqPXc6da9C

nodejs/views/profile.ejs

@@ -351,7 +351,7 @@
 				<i class="fa-solid fa-users-viewfinder"></i>
 				My groups
 				<div class="float-end">
-					<a href="/docs/ldap" class="text-reset me-2" title="Help"><i class="fa-solid fa-circle-question"></i></a>
+					<a href="/docs/accounts" class="text-reset me-2" title="Help"><i class="fa-solid fa-circle-question"></i></a>
 					<i class="fa-solid fa-arrows-up-down"></i>
 				</div>
 			</div>
@@ -397,7 +397,7 @@
 				<i class="fa-solid fa-people-group"></i>
 				Members of <span id="personal-group-uid-label"></span>'s group
 				<div class="float-end">
-					<a href="/docs/ldap" class="text-reset me-2" title="Help"><i class="fa-solid fa-circle-question"></i></a>
+					<a href="/docs/accounts" class="text-reset me-2" title="Help"><i class="fa-solid fa-circle-question"></i></a>
 					<i class="fa-solid fa-arrows-up-down"></i>
 				</div>
 			</div>
@@ -613,7 +613,7 @@
 	<div class="col-md-4">
 		<div class="card shadow-lg">
 			<div class="card-header"><i class="fa-solid fa-plus"></i> New API Token
-				<a href="/docs/api" class="text-reset float-end" title="Help"><i class="fa-solid fa-circle-question"></i></a>
+				<a href="/docs/api-tokens" class="text-reset float-end" title="Help"><i class="fa-solid fa-circle-question"></i></a>
 			</div>
 			<div class="card-header actionMessage" style="display:none"></div>
 			<div class="card-body">