fix: persist and correctly forward appointment attachments to insurance claims

- Add "surg ext" alias mapping to D7210 in the AI CDT lookup.
- Add GET/DELETE endpoints for appointment attachments, and load existing
  attachments in the appointment edit modal (they were uploaded correctly
  but never re-fetched, so they appeared to vanish on reopen).
- Fix claim-form.tsx so previously-saved appointment attachments are always
  loaded (even when a claim already exists) instead of only when creating a
  brand-new claim, preventing them from being silently wiped on save.
- Merge existing appointment attachments into every insurance submit handler
  (MassHealth, CCA, DDMA, UnitedDH, TuftsSCO) so Selenium submission always
  includes files saved earlier via the Schedule editor, not just files
  uploaded in the current claim-form session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/Backend/src/ai/cdt-lookup.ts

@@ -125,6 +125,7 @@ const ALIAS_MAP: Record<string, string> = {
   "simple extraction":     "extraction erupted",
   "surgical extraction":   "extraction bone",
   "surgical ext":          "extraction bone",
+  "surg ext":              "extraction bone",
   "baby tooth ext":        "extraction primary",
   "baby tooth extraction": "extraction primary",
   "primary tooth ext":     "extraction primary",
@@ -211,6 +212,7 @@ const DIRECT_CODE_MAP: Record<string, string> = {
   "primary tooth ext":      "D7111",
   "surgical extraction":    "D7210",
   "surgical ext":           "D7210",
+  "surg ext":               "D7210",
   "soft tissue impaction":  "D7220",
   "partial bony":           "D7230",
   "complete bony":          "D7240",