chore(archive): preserve KNELServerBuild remainder + layout notes [#474]

Archive the non-ported remainder of the legacy KNELServerBuild repo
under archive/KNELServerBuild/ with its original structure intact,
completing the legacy repo merge for everything except the live
LibreNMS patterns (ported in the previous commit).

Exclusions:
- .git history (superseded; legacy repo remains at its original path)
- ported files (Agents/librenms, Modules/OAM/oam-librenms.sh,
  ConfigFiles/SNMP/snmp-sudo.conf)
- vendored KNELShellFramework tree (byte-identical duplicate of the
  copy already vendored at vendor/ in this repo)
- SSH authorized-keys files (live access-control material; carrying
  them in an archive invites drift — key policy lives elsewhere)

The whole tree is skip-listed in tests/shellcheck.sh (archived legacy
code, not maintained — same standing as vendor/); check-rules.sh
already prunes archive/. Rule 9 (conflict markers) now also excludes
archive/ staged files: preserved-verbatim legacy scripts contain
decorative "====" banners that false-positive as conflict markers
(same archive exclusion precedent as rule 11).

AGENTS.md: note archive/KNELServerBuild and oam/librenms-agent in the
Repository Layout, and fix the stale KNELIAC path to
/home/reachableceo/projects/KNEL/KNELIAC.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

archive/KNELServerBuild/dns-cluster-setup/sync-zones.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/bash
+#
+# sync-zones.sh — rsync-based zone replication from primary to secondary
+#
+# Runs on the SECONDARY (netinfra-02). Syncs the zones/ directory from the
+# primary (netinfra-01) every 60 seconds. When a zone file changes, Technitium
+# detects the modification and reloads automatically.
+#
+# This is used instead of AXFR-based zone transfer because Technitium's zone
+# transfer mechanism uses port 53 (standard DNS), but on the netinfra hosts
+# port 53 is Pi-hole and Technitium is on port 5300. rsync-based replication
+# avoids the port conflict entirely.
+#
+# Install as a systemd service/timer or run via cron:
+#   * * * * * /home/localuser/services/technitium/sync-zones.sh
+#
+set -uo pipefail
+
+PRIMARY_HOST="${PRIMARY_HOST:-pfv-netinfra-01.knel.net}"
+CONFIG_DIR="${CONFIG_DIR:-/home/localuser/services/technitium/config}"
+ZONE_DIR="$CONFIG_DIR/zones"
+LOCK_FILE="/tmp/technitium-zone-sync.lock"
+LOG_FILE="${LOG_FILE:-/home/localuser/services/technitium/sync.log}"
+
+log() { printf '[%s] %s\n' "$(date +%H:%M:%S)" "$*" >> "$LOG_FILE"; }
+
+# Prevent overlapping runs
+exec 9>"$LOCK_FILE" || exit 0
+flock -n 9 || { log "another sync is running; skipping"; exit 0; }
+
+mkdir -p "$ZONE_DIR"
+
+# rsync zones from primary. Use --temp-dir to avoid partial writes being
+# picked up by Technitium, and --delete to remove zones deleted on primary.
+log "Syncing zones from $PRIMARY_HOST..."
+if rsync -az --delete --temp-dir=/tmp \
+   "${PRIMARY_HOST}:$ZONE_DIR/" "$ZONE_DIR/" >> "$LOG_FILE" 2>&1; then
+  zone_count=$(ls "$ZONE_DIR" | wc -l)
+  log "Sync complete: $zone_count zones"
+else
+  log "ERROR: rsync failed (rc=$?)"
+  exit 1
+fi