add backup_output_bytes metric and cloudsync_transferred_bytes to backup dashboard

- All 7 backup CronJobs now push backup_output_bytes (file size after backup)
- Cloud Sync monitor parses rclone transfer stats into cloudsync_transferred_bytes
- Grafana dashboard: new Output (MiB) table column, Output Size Trend panel,
  Write Throughput panel, Cloud Sync Transfer Volume bargauge
- All timeseries panels use points-only draw style (discrete backup snapshots)
- etcd backup restructured: init_container for etcdctl (distroless image),
  busybox sidecar for metrics push + purge, ClusterFirstWithHostNet DNS
- Fixed pre-existing curl missing in postgres:16.4-bullseye (immich, dbaas PG)
- Fixed grep -oP not available in alpine/busybox (cloud sync monitor)

stacks/redis/modules/redis/main.tf

@@ -305,9 +305,11 @@ resource "kubernetes_cron_job_v1" "redis-backup" {
                 echo "written: $(( (_wb1 - _wb0) / 1048576 )) MiB"
                 echo "output:  $(ls -lh /backup/redis-$$TIMESTAMP.rdb | awk '{print $5}')"
 
+                _out_bytes=$(stat -c%s /backup/redis-$TIMESTAMP.rdb)
                 wget -qO- --post-data "backup_duration_seconds $${_dur}
                 backup_read_bytes $(( _rb1 - _rb0 ))
                 backup_written_bytes $(( _wb1 - _wb0 ))
+                backup_output_bytes $${_out_bytes}
                 backup_last_success_timestamp $(date +%s)
                 " "http://prometheus-prometheus-pushgateway.monitoring:9091/metrics/job/redis-backup" || true
               EOT