feat(iace): Klaerungen MVP — Phase 1

New page "Klaerungen" between Massnahmen and Verifikation.

Backend:
- internal/iace/clarifications.go: Clarification struct + ClarificationAnswer +
  BuildProjectClarifications() — aggregates pattern-level + manufacturer-
  level questions from collectAllPatterns + GetManufacturerSafetyFeatures.
  Deterministic IDs ("pattern:HP1640:0", "manuf:fanuc:dual-check-safety-dcs:1")
  so persisted answers survive every re-init.
- internal/api/handlers/iace_handler_clarifications.go:
  - GET /projects/:id/clarifications returns aggregated list with affected
    hazard names + persisted answer state, sorted (open first).
  - POST /projects/:id/clarifications/:cid/answer writes status/answer/
    reasoning/answered_by/answered_at to project.metadata.clarification_-
    answers — no DB schema change.

Frontend:
- admin-compliance/app/sdk/iace/layout.tsx: new "Klaerungen" nav item.
- app/sdk/iace/[projectId]/clarifications/page.tsx: table grouped by
  source (FANUC / Pattern HP1640 / …), Filter Offen/Beantwortet/Alle,
  search field, Antwort-Modal with status/answer/Begruendung/Bearbeiter.

A clarification answered once applies to ALL referenced hazards — the
operator no longer has to answer the same FANUC DCS question on 48
mechanical hazards individually.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/iace/layout.tsx

@@ -14,6 +14,7 @@ const IACE_NAV_ITEMS = [
   { id: 'components', label: 'Komponenten', href: '/components', icon: 'cube' },
   { id: 'hazards', label: 'Hazard Log', href: '/hazards', icon: 'warning' },
   { id: 'mitigations', label: 'Massnahmen', href: '/mitigations', icon: 'shield' },
+  { id: 'clarifications', label: 'Klärungen', href: '/clarifications', icon: 'chat' },
   { id: 'verification', label: 'Verifikation', href: '/verification', icon: 'check' },
   { id: 'evidence', label: 'Nachweise', href: '/evidence', icon: 'document' },
   { id: 'tech-file', label: 'CE-Akte', href: '/tech-file', icon: 'folder' },