feat(sprint-6): Phase 4 — Immutable audit log
- V8 migration: audit_events table (JSONB metadata, immutable by design)
- AuditEvent entity + AuditEventType enum (18 event types)
- AuditService: log events, paginated query, PDF export
- AuditController: GET /api/v1/audit (paginated, filtered), GET export
- AuditEventRepository with JPQL filtered queries
- Frontend: /audit-log page (read-only, filterable, timezone-aware)
- PDF export button for Behörde inspections
- Sidebar: 'Protokoll' under new Compliance section
- PdfReportGenerator: generateAuditReport method added
- 10-year retention, REVOKE DELETE documented
- Full i18n (de/en) with 18 event type translations
Patrick Plate
05933a08ca