v1.2.2: Add Healthcare specialization, mark cancelled courses, rename Digital Marketing

Apply the J27 (5/6/2026) Stern specialization sheet:

- Add Healthcare (HCR) as the 15th specialization, with HCR cross-listings on
  spr2-health-medical, spr3-analytics-ml, sum2-social-media (renamed), and
  fall1-managing-change. 10 credits available, no required-course gate.
- Rename sum2-social-media to "Digital Marketing Strategy in Practice";
  replace its description with new MSKCC-anchored content; clear instructor
  pending confirmation of new lead.
- Switch from delete-and-replace to the previously-unused cancelled flag
  (Approach B): mark spr5-customer-insights cancelled, add Managing Growing
  Companies back to Summer Set 2 as a cancelled placeholder per the printed
  sheet.
- Update data integrity tests: course count 46 -> 47, spec count 14 -> 15;
  per-spec "across sets" helper now filters cancelled courses so future
  cancellations trigger an obvious assertion failure (BRM 6 -> 5,
  MKT 7 -> 6, HCR 4 new).
- Replace hardcoded 14 in optimizer.test.ts with SPECIALIZATIONS.length.

app/src/data/specializations.ts

@@ -9,6 +9,7 @@ export const SPECIALIZATIONS: Specialization[] = [
   { id: 'FIN', name: 'Finance', abbreviation: 'FIN' },
   { id: 'FIM', name: 'Financial Instruments and Markets', abbreviation: 'FIM' },
   { id: 'GLB', name: 'Global Business', abbreviation: 'GLB' },
+  { id: 'HCR', name: 'Healthcare', abbreviation: 'HCR' },
   { id: 'LCM', name: 'Leadership and Change Management', abbreviation: 'LCM' },
   { id: 'MGT', name: 'Management', abbreviation: 'MGT' },
   { id: 'MKT', name: 'Marketing', abbreviation: 'MKT' },