feat: UI redesign (CSS system, DNS widget, Traefik dashboard widget)

- Replace base.html style block with full CSS design system using custom properties (dark theme, cards, tables, badges, dots, widgets)
- Add DNS blueprint (fablednetmon/dns/) with /dns/ and /dns/rows routes + templates
- Add Traefik /widget route and widget.html fragment for dashboard
- Update dashboard: DNS + Traefik widgets, traefik_enabled config detection
- Update all templates to use new CSS classes (page-title, section-title, card-flush, table, badge-*, dot-*, btn-*)
- Register dns_bp in app.py

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

fablednetmon/templates/auth/setup.html

@@ -3,8 +3,8 @@
 {% block content %}
 <div style="max-width:400px;margin:4rem auto;">
     <div class="card">
-        <h2 style="margin-bottom:0.5rem;color:#c0c0ff;">First-Run Setup</h2>
-        <p style="margin-bottom:1.5rem;color:#8080a0;font-size:0.9rem;">Create the initial admin account.</p>
+        <h2 class="page-title" style="margin-bottom:0.5rem;">First-Run Setup</h2>
+        <p style="margin-bottom:1.5rem;color:var(--text-muted);font-size:0.9rem;">Create the initial admin account.</p>
         <form method="post" action="/setup">
             <div class="form-group">
                 <label>Username</label>
@@ -18,7 +18,7 @@
                 <label>Password</label>
                 <input type="password" name="password" required>
             </div>
-            <button type="submit">Create Admin Account</button>
+            <button type="submit" class="btn">Create Admin Account</button>
         </form>
     </div>
 </div>