Enhance debug logging for Passkey Registration options

Add detailed debug statements in the registrieren.vue component to validate the complete options structure during Passkey registration. Update the register-passkey API to simplify the options return process, eliminating unnecessary serialization while maintaining comprehensive logging of the options details for improved troubleshooting.

pages/registrieren.vue

@@ -443,6 +443,28 @@ const handleRegisterWithPasskey = async () => {
       console.error('[DEBUG] Options missing challenge:', JSON.stringify(pre.options, null, 2))
       throw new Error('Ungültige WebAuthn-Options vom Server')
     }
+    
+    // Debug: Prüfe die vollständige Options-Struktur
+    console.log('[DEBUG] Full options structure check:', {
+      hasChallenge: !!pre.options.challenge,
+      challengeValue: pre.options.challenge?.substring(0, 20) + '...',
+      challengeType: typeof pre.options.challenge,
+      hasRp: !!pre.options.rp,
+      rpId: pre.options.rp?.id,
+      rpName: pre.options.rp?.name,
+      hasUser: !!pre.options.user,
+      userId: pre.options.user?.id ? 'present' : 'missing',
+      userIdType: typeof pre.options.user?.id,
+      userName: pre.options.user?.name,
+      userDisplayName: pre.options.user?.displayName,
+      hasPubKeyCredParams: !!pre.options.pubKeyCredParams,
+      pubKeyCredParamsCount: pre.options.pubKeyCredParams?.length,
+      hasAuthenticatorSelection: !!pre.options.authenticatorSelection,
+      timeout: pre.options.timeout,
+      timeoutType: typeof pre.options.timeout,
+      allKeys: Object.keys(pre.options),
+      optionsStringified: JSON.stringify(pre.options).substring(0, 200) + '...'
+    })
 
     console.log('[DEBUG] Calling startRegistration...')
     console.log('[DEBUG] Full options object (will be encoded in QR code for Cross-Device):', JSON.stringify(pre.options, null, 2))