feat: drag-and-drop dashboard editing, alert dynamic fields

- Replace up/down arrow reorder buttons on dashboard edit page with
  SortableJS drag handles; add POST /d/<id>/edit/reorder endpoint
  accepting ordered widget ID array
- Add {% block extra_scripts %} hook to base.html for page-specific JS
- Add dynamic alert rule field loading via HTMX partial (_rule_fields)
  so metric/threshold fields update when source is changed
- Add docs/plugins/index.yaml.example showing catalog index format

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fabledscryer/templates/base.html

@@ -5,6 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>{% block title %}Fabled Scryer{% endblock %}</title>
     <script src="https://unpkg.com/htmx.org@2.0.4/dist/htmx.min.js"></script>
+    <script src="https://cdn.jsdelivr.net/npm/chart.js@4.4.4/dist/chart.umd.min.js"></script>
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Libertinus+Serif:ital,wght@0,400;0,600;0,700;1,400&display=swap" rel="stylesheet">
@@ -214,12 +215,14 @@ textarea { resize: vertical; }
     </a>
     <a href="/">Dashboard</a>
     <a href="/hosts/">Hosts</a>
+    <a href="/hosts/uptime">Uptime</a>
     <a href="/ping/">Ping</a>
     <a href="/dns/">DNS</a>
     <a href="/alerts/">Alerts</a>
     <a href="/ansible/">Ansible</a>
     {% if session.user_role == 'admin' %}
     <a href="/settings/">Settings</a>
+    <a href="/audit/">Audit</a>
     {% endif %}
     <a href="/logout" class="nav-end">{{ session.username }}</a>
 </nav>
@@ -351,5 +354,7 @@ function setTimeRange(val) {
 }());
 </script>
 
+{% block extra_scripts %}{% endblock %}
+
 </body>
 </html>