fix(escalations): Tenant/User-ID Defaults + Routing-Klarheit

- escalations/route.ts: X-Tenant-Id + X-User-Id Default-Header ergaenzt,
  X-User-Id aus Request weitergeleitet
- escalation_routes.py: DEFAULT_TENANT_ID Konstante (9282a473-...) statt 'default'
- test_escalation_routes.py: vollstaendige Test-Suite ergaenzt (+337 Zeilen)
- main.go + escalation_handlers.go: DEPRECATED-Kommentare — UCCA-Escalations
  bleiben fuer Assessment-Review, Haupt-Escalation-System ist Python-Backend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin-compliance/app/api/sdk/v1/escalations/[[...path]]/route.ts

@@ -22,6 +22,8 @@ async function proxyRequest(
   try {
     const headers: HeadersInit = {
       'Content-Type': 'application/json',
+      'X-Tenant-Id': '9282a473-5c95-4b3a-bf78-0ecc0ec71d3e',
+      'X-User-Id': 'admin',
     }
 
     const authHeader = request.headers.get('authorization')
@@ -34,6 +36,11 @@ async function proxyRequest(
       headers['X-Tenant-Id'] = tenantHeader
     }
 
+    const userIdHeader = request.headers.get('x-user-id')
+    if (userIdHeader) {
+      headers['X-User-Id'] = userIdHeader
+    }
+
     const fetchOptions: RequestInit = {
       method,
       headers,