feat(security): ABAC P2/P3-lite — BIG-nummer redaction, authz audit, guard; clear dev audit

- fix(deps): pin @babel/core ^7.29.7 via overrides → npm audit 0 (dev+prod),
  no --force / no Angular downgrade; README corrected
- feat(brief): field-level PII reveal (PRD-0002 §5c) — CaseContext BIG-nummer
  ships masked; step-up-stubbed (X-Step-Up), audited POST /brief/reveal-bignummer
  unmasks it; drafter-only capability, deny-by-default. Realized on the BIG-nummer
  (no BSN on the wire)
- feat(authz): no-PII AuditAuthz log for reveal attempts + org-admin denials (§8)
- feat(routes): wire capabilityGuard('orgtemplate:edit') onto brief/huisstijl (§6)
- test: backend +5 (Authz + reveal endpoint), FE +3 (adapter boundary, store swap)
- docs: PRD-0002 §5c/§9, WP-18 follow-up, README

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -64,6 +64,7 @@
   },
   "comment-overrides": "Pin patched versions of vulnerable DEV/BUILD-only transitive deps (Storybook + build chain). The shipped app already audits clean; this clears the dev-tooling advisories without downgrading Angular 22.",
   "overrides": {
+    "@babel/core": "^7.29.7",
     "picomatch": "^4.0.4",
     "esbuild": "^0.28.1",
     "http-proxy-middleware": "^3.0.7",