Add workspace cleanup stage to prevent corruption issues

- Add Cleanup stage at pipeline start to wipe workspace before checkout
- Prevents 'corrupt .git repository' errors from stale build artifacts
- Uses disableDeferredWipeout for thorough cleanup

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Entire-Checkpoint: f6767c4eba2c
Signed-off-by: twi-devel <torsten.wierschin@life-maps.com>

Jenkinsfile

@@ -23,6 +23,15 @@ pipeline {
   }
 
   stages {
+    stage('Cleanup') {
+      steps {
+        script {
+          echo "Cleaning workspace to avoid corruption issues..."
+          cleanWs deleteDirs: true, disableDeferredWipeout: true
+        }
+      }
+    }
+
     stage('Checkout') {
       steps {
         checkout scm