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/shared/schemas/results/PdfFileCreateManyResult.schema.ts

@@ -0,0 +1,4 @@
+import * as z from 'zod';
+export const PdfFileCreateManyResultSchema = z.object({
+  count: z.number()
+});