feat: add initial_delay_minutes to reconciler for LB stagger 🕐

Configurable startup delay before the first reconciliation pass so that
multiple receivers behind a load balancer can be offset without relying
on container start order (which is lost on reboot). Set to half the
interval on the secondary receiver — e.g. interval 60m → delay 30m.
Default is 0 (no change to existing behaviour). Stop event is respected
during the delay so the worker shuts down cleanly even mid-wait.

directdnsonly/config/app.yml

@@ -14,6 +14,8 @@ app:
 #  enabled: true
 #  dry_run: true             # log orphans but do NOT queue deletes — safe first-run mode
 #  interval_minutes: 60
+#  initial_delay_minutes: 0  # stagger first run when running multiple receivers behind a LB
+#                            # e.g. receiver-1: 0, receiver-2: 30 (half the interval)
 #  verify_ssl: true          # set false for self-signed DA certs
 #  ipp: 1000                 # items per page when polling DA (default 1000)
 #  directadmin_servers: