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/Backend/src/routes/selenium-settings.ts

@@ -0,0 +1,42 @@
+import { Router, Request, Response } from "express";
+import { prisma as db } from "@repo/db/client";
+
+const router = Router();
+
+// GET /api/selenium-settings
+router.get("/", async (req: Request, res: Response): Promise<any> => {
+  try {
+    const userId = req.user?.id;
+    if (!userId) return res.status(401).json({ message: "Unauthorized" });
+
+    const settings = await db.seleniumSettings.findUnique({ where: { userId } });
+    return res.status(200).json({ paymentGroupId: settings?.paymentGroupId ?? "" });
+  } catch (err) {
+    return res.status(500).json({ error: "Failed to fetch Selenium settings", details: String(err) });
+  }
+});
+
+// PUT /api/selenium-settings
+router.put("/", async (req: Request, res: Response): Promise<any> => {
+  try {
+    const userId = req.user?.id;
+    if (!userId) return res.status(401).json({ message: "Unauthorized" });
+
+    const { paymentGroupId } = req.body;
+    if (typeof paymentGroupId !== "string") {
+      return res.status(400).json({ message: "paymentGroupId must be a string" });
+    }
+
+    const settings = await db.seleniumSettings.upsert({
+      where: { userId },
+      update: { paymentGroupId: paymentGroupId.trim() },
+      create: { userId, paymentGroupId: paymentGroupId.trim() },
+    });
+
+    return res.status(200).json({ paymentGroupId: settings.paymentGroupId });
+  } catch (err) {
+    return res.status(500).json({ error: "Failed to save Selenium settings", details: String(err) });
+  }
+});
+
+export default router;