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/[projectId]/page.tsx

@@ -5,6 +5,7 @@ import Link from 'next/link'
 import { useParams } from 'next/navigation'
 import { SuggestedNorms } from './_components/SuggestedNorms'
 import { ComplianceAlerts } from './_components/ComplianceAlerts'
+import { VariantPanel } from './_components/VariantPanel'
 
 interface ProjectOverview {
   id: string
@@ -15,6 +16,8 @@ interface ProjectOverview {
   completeness_pct: number
   created_at: string
   updated_at: string
+  parent_project_id?: string | null
+  parent_project_name?: string
   metadata?: { limits_form?: Record<string, unknown> }
   risk_summary?: {
     critical?: number
@@ -125,12 +128,26 @@ export default function ProjectOverviewPage() {
       const stepsComplete = [hasLimits, hasComponents, hasHazards, hasMitigations].filter(Boolean).length
       const completeness = Math.round((stepsComplete / 6) * 100)
 
+      // If this is a variant, resolve parent project name
+      let parentName: string | undefined
+      if (json.parent_project_id) {
+        try {
+          const parentRes = await fetch(`/api/sdk/v1/iace/projects/${json.parent_project_id}`)
+          if (parentRes.ok) {
+            const parentJson = await parentRes.json()
+            parentName = parentJson.machine_name
+          }
+        } catch { /* ignore */ }
+      }
+
       setProject({
         ...json,
         completeness_pct: completeness,
         component_count: compCount,
         hazard_count: hazCount,
         mitigation_count: mitCount,
+        parent_project_id: json.parent_project_id || null,
+        parent_project_name: parentName,
         metadata: json.metadata,
         risk_summary: {
           critical: rs.critical || 0,
@@ -334,6 +351,13 @@ export default function ProjectOverviewPage() {
       {/* Compliance Alerts */}
       <ComplianceAlerts projectId={projectId} />
 
+      {/* Variant Management */}
+      <VariantPanel
+        projectId={projectId}
+        parentProjectId={project.parent_project_id}
+        parentProjectName={project.parent_project_name}
+      />
+
       {/* Suggested Norms */}
       <SuggestedNorms projectId={projectId} />