chore(backup-system): consolidar config rclone en Infisical (mega+b2)

El bloque [b2] ya vive en RCLONE_CONF (Infisical /backup-system); los 3
CronJobs vuelven a rclone-conf-infisical y se elimina el secret
out-of-band rclone-conf-b2.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backup-system/cronjob-backup-verify.yaml

@@ -36,10 +36,10 @@ spec:
                 - mountPath: /scripts
                   name: scripts
           volumes:
-            # rclone-conf-b2: secret out-of-band con mega+b2 (verify comprueba ambos)
+            # RCLONE_CONF (Infisical /backup-system) contiene mega+b2 desde 2026-07-15
             - name: rclone-conf
               secret:
-                secretName: rclone-conf-b2
+                secretName: rclone-conf-infisical
                 items:
                   - key: RCLONE_CONF
                     path: rclone.conf