feat: add Check MH Payment automation and MH Paid column

- Add selenium_MHPaymentCheckWorker.py: logs into MassHealth portal, navigates to Search Claims, enters claim number, extracts totalPaidAmount from results table
- Register /mh-payment-check endpoint in Selenium agent
- Add mhPaidAmount field to Payment model with migration
- Add PATCH /api/payments/:id/mh-payment-check backend route: fetches MH credentials, calls selenium, stores result
- Add Claim No. column (MassHealth claim number) as first data column in payments table
- Move Payment ID and Claim ID columns to end of table
- Add MH Paid column showing mhPaidAmount in green
- Wire Check MH Payment button to call API for each selected payment and refresh table

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

packages/db/prisma/migrations/20260506000000_add_mh_paid_amount/migration.sql

@@ -0,0 +1 @@
+ALTER TABLE "Payment" ADD COLUMN "mhPaidAmount" DECIMAL(10,2);

packages/db/prisma/schema.prisma

@@ -330,6 +330,7 @@ model Payment {
   totalPaid     Decimal       @default(0.00) @db.Decimal(10, 2)
   totalAdjusted Decimal       @default(0.00) @db.Decimal(10, 2)
   totalDue      Decimal       @db.Decimal(10, 2)
+  mhPaidAmount  Decimal?      @db.Decimal(10, 2)
   status        PaymentStatus @default(PENDING)
   notes         String?
   icn           String?