Enhance debug logging and Cross-Device support for Passkey Registration

Update the registrieren.vue component to include detailed debug statements for the Cross-Device authentication flow, specifically during QR-Code generation. Improve logging in the register-passkey-options and register-passkey APIs to capture request details such as user agent and IP address, aiding in troubleshooting. Additionally, introduce a new function to retrieve pre-registration data, enhancing the overall registration process and compliance with Cross-Device requirements.

server/api/auth/register-passkey-options.options.js

@@ -4,10 +4,17 @@ export default defineEventHandler(async (event) => {
   const requestOrigin = getHeader(event, 'origin')
   const { origin: webauthnOrigin } = getWebAuthnConfig()
   
-  console.log('[DEBUG] OPTIONS preflight request received', {
-    origin: requestOrigin,
+  const userAgent = getHeader(event, 'user-agent')
+  const ip = getHeader(event, 'x-forwarded-for') || getHeader(event, 'x-real-ip') || 'unknown'
+  
+  console.log('[DEBUG] ===== OPTIONS preflight for /api/auth/register-passkey-options =====')
+  console.log('[DEBUG] OPTIONS Request Details:', {
+    origin: requestOrigin || 'none',
     webauthnOrigin,
-    timestamp: new Date().toISOString()
+    userAgent: userAgent?.substring(0, 100) || 'none',
+    ip,
+    timestamp: new Date().toISOString(),
+    note: 'OPTIONS Preflight für Passkey Registration Options'
   })
 
   // CORS-Header für Cross-Device Authentication