feat: add Selenium Settings page to configure paymentGroupId per office

Adds a new Settings → Advanced → Selenium Settings page where the office
name (paymentGroupId) used in United/DentalHub portal dropdowns can be
configured without touching code. Previously hardcoded as "Summit Dental
Care"; now injected from DB into the three United workers at job dispatch.

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

apps/Frontend/src/components/layout/sidebar.tsx

@@ -30,6 +30,7 @@ import {
   Building2,
   Timer,
   BookOpen,
+  MonitorCog,
   GraduationCap,
   ShoppingCart,
   Search,
@@ -291,6 +292,11 @@ export function Sidebar() {
             path: "/settings/aichat",
             icon: <Bot className="h-4 w-4 text-gray-400" />,
           },
+          {
+            name: "Selenium Settings",
+            path: "/settings/selenium",
+            icon: <MonitorCog className="h-4 w-4 text-gray-400" />,
+          },
         ],
       },
     ],