CCM-15826: Fix dependency audit critical warning

Removed the unnecessary workspace-local ts-jest dependency from frontend/ so the package now uses the shared root test tooling, in line with the repo’s AGENTS.md guidance to centralise dev tooling unless a local override is strictly needed.
This eliminated the only dependency path that introduced vulnerable handlebars@4.7.8, resolving the critical npm audit finding without changing frontend runtime behaviour.
Validated with npm audit, npm ls handlebars ts-jest --all, frontend build, lint, typecheck, and test:unit.
Ran root pre-commit checks; the full run was blocked by unrelated unstaged workspace changes, but the changed files passed targeted pre-commit validation.
AI assistance was used to prepare this change.

Author: m-houston

.gitignore

@@ -24,6 +24,7 @@ dist
 .reports
 /.idea
 **/.next
+.tsconfig.tsbuildinfo
 
 .env
 /.envrc

frontend/package.json

@@ -22,7 +22,6 @@
     "eslint-config-next": "^15.4.6",
     "prettier": "^3.5.3",
     "sass": "^1.86.0",
-    "ts-jest": "^29.4.6",
     "typescript": "^5.9.3"
   },
   "name": "@supplier-config/frontend",