feat: add PreAuth tab, preauth selenium flow, and PreAuth No column

- Insurance Forms modal: split into Insurance Claim / PreAuth tabs
- PreAuth tab: same patient info + service lines, no toggle/direct combos
- Excluded Recalls & New Patients, Composite Fillings (Front/Back), Pedo from PreAuth combos
- Extractions: replaced Simple/Surg/Baby Teeth EXT with Full Bony EXT (D7240)
- MH PreAuth button: rewritten selenium worker to use masshealth-dental.org,
  selects Dental Prior Authorization (2nd option), skips Date of Service field
- agent.py: convert pdf_path to pdf_url for /claim-pre-auth endpoint
- nginx + Express: raise body size limit to 50mb (fix 413 errors)
- DB schema: appointmentId optional on Claim, add preAuthNumber field, add PREAUTH status
- Backend: create PREAUTH claim record on preauth submit, save preAuthNumber on completion
- Claims table: add PreAuth No column (blue) next to Claim No

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

packages/db/generated/prisma/schema.prisma

@@ -197,7 +197,7 @@ model AppointmentProcedure {
 model Claim {
   id                 Int                @id @default(autoincrement())
   patientId          Int
-  appointmentId      Int
+  appointmentId      Int?
   userId             Int
   staffId            Int
   patientName        String
@@ -212,10 +212,11 @@ model Claim {
   updatedAt          DateTime           @updatedAt
   status             ClaimStatus        @default(PENDING)
   claimNumber        String?
+  preAuthNumber      String?
   npiProviderId      Int?
 
   patient     Patient      @relation(fields: [patientId], references: [id], onDelete: Cascade)
-  appointment Appointment  @relation(fields: [appointmentId], references: [id], onDelete: Cascade)
+  appointment Appointment? @relation(fields: [appointmentId], references: [id], onDelete: Cascade)
   user        User?        @relation(fields: [userId], references: [id])
   staff       Staff?       @relation("ClaimStaff", fields: [staffId], references: [id])
   npiProvider NpiProvider? @relation(fields: [npiProviderId], references: [id])
@@ -231,6 +232,7 @@ enum ClaimStatus {
   CANCELLED
   REVIEW
   VOID
+  PREAUTH
 }
 
 enum MissingTeethStatus {