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>

nginx.conf

@@ -2,6 +2,8 @@ server {
     listen 80;
     server_name _;
 
+    client_max_body_size 50m;
+
     # API requests → backend (Authorization header must be explicit or it gets stripped)
     location /api/ {
         proxy_pass http://localhost:5000;