feat: Variantenmanagement — Sub-Projekte mit GAP-Analyse

Backend:
- parent_project_id auf iace_projects (DB + Go Struct)
- POST/GET /variants + GET /variant-gap Endpoints
- GAP-Analyse: Differenz Hazards/Massnahmen/Kategorien

Frontend:
- VariantPanel auf Projekt-Uebersicht
- Variante erstellen Dialog
- Sidebar-Anzeige (Variantenanzahl / Basis-Link)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -108,12 +108,40 @@ export default function IACELayout({ children }: { children: React.ReactNode })
   const params = useParams()
   const projectId = params?.projectId as string | undefined
   const [projectName, setProjectName] = React.useState('')
+  const [variantInfo, setVariantInfo] = React.useState<{
+    parentProjectId?: string; parentName?: string; variantCount?: number
+  }>({})
 
   React.useEffect(() => {
     if (!projectId) return
     fetch(`/api/sdk/v1/iace/projects/${projectId}`)
       .then(r => r.ok ? r.json() : null)
-      .then(d => { if (d?.machine_name) setProjectName(d.machine_name) })
+      .then(async (d) => {
+        if (!d?.machine_name) return
+        setProjectName(d.machine_name)
+        // Resolve variant info
+        if (d.parent_project_id) {
+          try {
+            const pRes = await fetch(`/api/sdk/v1/iace/projects/${d.parent_project_id}`)
+            if (pRes.ok) {
+              const pj = await pRes.json()
+              setVariantInfo({ parentProjectId: d.parent_project_id, parentName: pj.machine_name })
+            } else {
+              setVariantInfo({ parentProjectId: d.parent_project_id })
+            }
+          } catch { setVariantInfo({ parentProjectId: d.parent_project_id }) }
+        } else {
+          // Check if this project has variants
+          try {
+            const vRes = await fetch(`/api/sdk/v1/iace/projects/${projectId}/variants`)
+            if (vRes.ok) {
+              const vj = await vRes.json()
+              const list = vj.variants || vj.projects || []
+              if (list.length > 0) setVariantInfo({ variantCount: list.length })
+            }
+          } catch { /* no variants endpoint yet */ }
+        }
+      })
       .catch(() => {})
   }, [projectId])
 
@@ -148,6 +176,21 @@ export default function IACELayout({ children }: { children: React.ReactNode })
                 {projectName}
               </p>
             )}
+            {variantInfo.parentProjectId && (
+              <Link
+                href={`/sdk/iace/${variantInfo.parentProjectId}`}
+                className="mt-1 flex items-center gap-1 text-[10px] text-orange-600 hover:text-orange-700 dark:text-orange-400 truncate"
+                title={variantInfo.parentName ? `Variante von: ${variantInfo.parentName}` : 'Variante'}
+              >
+                <svg className="w-3 h-3 flex-shrink-0" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M7 16V4m0 0L3 8m4-4l4 4" />
+                </svg>
+                Variante von: {variantInfo.parentName || 'Basis'}
+              </Link>
+            )}
+            {variantInfo.variantCount != null && variantInfo.variantCount > 0 && (
+              <p className="mt-1 text-[10px] text-gray-400">({variantInfo.variantCount} Varianten)</p>
+            )}
             <p className="text-[10px] text-gray-400 mt-0.5">CE-Compliance</p>
             <Link
               href="/sdk/iace/lines"