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>

src/app/shared/infrastructure/api-client.ts

@@ -1579,6 +1579,7 @@ export interface BriefDecisionsDto {
     canApprove?: boolean;
     canReject?: boolean;
     canSend?: boolean;
+    canRevealBigNummer?: boolean;
 }
 
 export interface BriefDto {