feat(iace): Customer-Standard-Reuse across customer's prior projects

[migration-approved]

Task #22. The IACE module is used by a single Maschinenhersteller, but
their plants land at many different end customers. When the safety expert
commissions the second or third plant at the same customer, whole classes
of mitigations (company-wide PPE rules, locked-out energy isolation,
customer-standard signage) are already in place there — but rediscovered
from scratch every project.

Migration 031: iace_projects.customer_name TEXT + partial index.
  The customer is stored as a plain text field rather than a normalised
  iace_customers table (option A from the design discussion). A proper
  customer-management screen can promote this to a FK later without
  data loss.

Backend store_customer_standards.go:
  - ListCustomerStandardSuggestions(projectID, includeVerified) collects
    mitigations from all non-archived prior projects sharing the same
    tenant_id AND case-insensitive customer_name. Aggregates by
    mitigation.name (since same-named measures from different prior
    projects collapse into one suggestion) and surfaces:
      • source_project_count + source_project_names
      • is_customer_standard / has_verified_instances flags
    includeVerified=false → strictly is_customer_standard=true
    includeVerified=true  → also status='verified'
  - ImportCustomerStandardSuggestion(projectID, name): for every prior
    (mitigation.name → hazard.name) pairing, finds matching hazards in
    the current project (by name) and ensures a customer-standard
    mitigation exists. New rows via CreateMitigation (idempotent through
    the UNIQUE(hazard_id, name) from migration 030); existing rows are
    flipped to is_relevant=true + is_customer_standard=true +
    status='verified' via UPDATE.

Routes:
  GET  /api/v1/iace/projects/:id/customer-standards?include_verified=
  POST /api/v1/iace/projects/:id/customer-standards/import   body {name}

Frontend:
  - New page /sdk/iace/[projectId]/customer-standards with:
      • empty-state hint pointing to Auftrag → Kundenname
      • per-suggestion checkbox + per-row Übernehmen button
      • bulk "N übernehmen" button
      • toggle "Auch verifizierte einbeziehen" widening the pool
      • per-suggestion source_project_count + status badges
  - Sidebar item "Kundenstandards" (building icon) placed between
    Verifikation and Nachweise.
  - Order-page now mirrors Auftraggeber.Firmenname into the top-level
    customer_name column on save, so the Reuse feature is fed
    automatically without a separate input field.

The same expert effect from migration 029's is_customer_standard flag —
"I already know it's covered, no evidence needed" — now becomes a
cross-project asset rather than a per-project annotation.

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

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

@@ -16,6 +16,7 @@ const IACE_NAV_ITEMS = [
   { 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: 'customer-standards', label: 'Kundenstandards', href: '/customer-standards', icon: 'building' },
   { id: 'evidence', label: 'Nachweise', href: '/evidence', icon: 'document' },
   { id: 'tech-file', label: 'CE-Akte', href: '/tech-file', icon: 'folder' },
 ]
@@ -67,6 +68,12 @@ function NavIcon({ icon, className }: { icon: string; className?: string }) {
           <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 12l2 2 4-4m6 2a9 9 0 11-18 0 9 9 0 0118 0z" />
         </svg>
       )
+    case 'building':
+      return (
+        <svg className={cls} fill="none" viewBox="0 0 24 24" stroke="currentColor">
+          <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 21V5a2 2 0 00-2-2H7a2 2 0 00-2 2v16m14 0H5m14 0h2m-16 0H3m4-4h2m-2-4h2m-2-4h2m4 8h2m-2-4h2m-2-4h2" />
+        </svg>
+      )
     case 'document':
       return (
         <svg className={cls} fill="none" viewBox="0 0 24 24" stroke="currentColor">