Enhance MemberTransferService and MemberTransferDialog with detailed debug logging

Added extensive debug logging to the MemberTransferService to track member transfer details, including logging the first few members and bulk data structure. Updated the MemberTransferDialog to clear login credentials upon loading and closing, improving user experience and ensuring a clean state for configuration loading. These enhancements aim to facilitate troubleshooting and provide better visibility into the member transfer process.

frontend/src/components/MemberTransferDialog.vue

@@ -172,7 +172,17 @@ export default {
   watch: {
     modelValue(newVal) {
       if (newVal) {
+        // WICHTIG: Felder sofort leeren, bevor Konfiguration geladen wird
+        this.loginCredentials = {
+          username: '',
+          password: '',
+          additionalField1: '',
+          additionalField2: ''
+        };
         this.loadSavedConfig();
+      } else {
+        // Beim Schließen auch leeren
+        this.resetForm();
       }
     }
   },