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>

packages/db/prisma/schema.prisma

@@ -51,6 +51,7 @@ model User {
   insuranceContacts     InsuranceContact[]
   patientConversations  PatientConversation[]
   labRxTemplates        LabRxTemplate[]
+  seleniumSettings      SeleniumSettings?
 }
 
 model Patient {
@@ -745,3 +746,13 @@ model CommissionBatchItem {
   @@unique([commissionBatchId, paymentId])
   @@index([paymentId])
 }
+
+model SeleniumSettings {
+  id             Int    @id @default(autoincrement())
+  userId         Int    @unique
+  paymentGroupId String @default("")
+
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@map("selenium_settings")
+}