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/app.py

@@ -87,6 +87,7 @@ def create_app(
     from .dashboard.routes import dashboard_bp
     from .hosts.routes import hosts_bp
     from .ping.routes import ping_bp
+    from .dns.routes import dns_bp
     from .alerts.routes import alerts_bp
     from .ansible.routes import ansible_bp
     from .settings.routes import settings_bp
@@ -95,6 +96,7 @@ def create_app(
     app.register_blueprint(dashboard_bp)
     app.register_blueprint(hosts_bp)
     app.register_blueprint(ping_bp)
+    app.register_blueprint(dns_bp)
     app.register_blueprint(alerts_bp)
     app.register_blueprint(ansible_bp)
     app.register_blueprint(settings_bp)