Fix cluster backup auto-confirm and confirmation Init

- Skip confirmation dialog in auto-confirm mode for cluster backup
- Call confirm.Init() to trigger auto-confirm message

.dbbackup.conf

@@ -0,0 +1,25 @@
+# dbbackup configuration
+# This file is auto-generated. Edit with care.
+
+[database]
+type = postgres
+host = 172.20.0.3
+port = 5432
+user = postgres
+database = postgres
+ssl_mode = prefer
+
+[backup]
+backup_dir = /root/source/dbbackup/tmp
+compression = 6
+jobs = 4
+dump_jobs = 2
+
+[performance]
+cpu_workload = balanced
+max_cores = 8
+
+[security]
+retention_days = 30
+min_backups = 5
+max_retries = 3