jenkins: clean stale JCasC files on startup

services/jenkins/helmrelease.yaml

@@ -79,6 +79,21 @@ spec:
             secretKeyRef:
               name: jenkins-oidc
               key: logoutUrl
+      customInitContainers:
+        - name: clean-jcasc-stale
+          image: alpine:3.20
+          imagePullPolicy: IfNotPresent
+          command:
+            - sh
+            - -c
+            - |
+              set -euo pipefail
+              rm -f /var/jenkins_home/casc_configs/*.yaml || true
+          securityContext:
+            runAsUser: 0
+          volumeMounts:
+            - name: jenkins-home
+              mountPath: /var/jenkins_home
       initScripts:
         oidc.groovy: |
           import hudson.util.Secret