feat: rename to FabledScryer, multi-dashboard system, plugin management, branding

- Rename package fablednetmon → fabledscryer throughout
- Multi-dashboard: ownership, per-user defaults, HTMX edit (add/remove/reorder)
- Read-only share tokens scoped to individual dashboards
- Dashboard edit is HTMX-driven (no page reloads)
- Plugin management system: remote catalog, download/install, hot-reload, in-app restart
- plugin_index.py: fetch/cache remote index.yaml; default URL → bvandeusen/fabledscryer-plugins
- plugin_manager.py: download_and_install_plugin, hot_reload_plugin, restart_app
  - ZIP extraction handles GitHub archive formats (name-v1.0.0/, name-main/)
- Settings split into tabbed sections: General, Notifications, Ansible, Plugins
- Plugins tab: catalog browser (HTMX), install/activate/update/restart actions
- UI/branding: dark palette (#07071a), crystal ball SVG logo, animated star field,
  Libertinus Serif applied to headings, nav, labels, and section titles
- Widget registry (core/widgets.py) for dashboard plugin integration
- UPS widget.html (dashboard card) and settings/_tabs.html include
- Migrations 0005–0008: dashboards, is_default, ownership, share tokens
- docs/plugins/: writing-a-plugin.md updated with publishing guide,
  index.yaml.example template for fabledscryer-plugins repo

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

fabledscryer/templates/settings/_tabs.html

@@ -0,0 +1,16 @@
+{# settings/_tabs.html — include at top of each settings section #}
+<h1 class="page-title">Settings</h1>
+<div style="display:flex;gap:0;border-bottom:1px solid var(--border-mid);margin-bottom:1.5rem;">
+  {% set tabs = [
+    ("general",       "General",        "/settings/general/"),
+    ("notifications", "Notifications",  "/settings/notifications/"),
+    ("ansible",       "Ansible",        "/settings/ansible/"),
+    ("plugins",       "Plugins",        "/settings/plugins/"),
+  ] %}
+  {% for key, label, href in tabs %}
+  <a href="{{ href }}"
+     style="padding:0.6rem 1.1rem;font-size:0.875rem;border-bottom:2px solid {{ 'var(--accent)' if active_tab == key else 'transparent' }};color:{{ 'var(--text)' if active_tab == key else 'var(--text-muted)' }};font-weight:{{ '500' if active_tab == key else 'normal' }};text-decoration:none;">
+    {{ label }}
+  </a>
+  {% endfor %}
+</div>