DEPOT logging: add Telemt fleet monitoring via Zabbix

Install and persist Grafana Zabbix plugin 6.5.0, provision the internal Zabbix datasource, and add a fleet dashboard modeled on client 02 Telemt panels.

Add an active-agent Zabbix 7 template plus a 30-second sanitized collector for active IP count/list, connections, traffic, and uptime. Active checks avoid inbound polling of client-private Docker hosts.

The exact Zabbix host names and required ZABBIX_API_TOKEN Portainer variable are documented. Compose validation passed on 10.0.0.6; the live plugin registered successfully under Grafana 13.1.0.

logging/zabbix-agent/zabbix-telemt-value

@@ -0,0 +1,30 @@
+#!/usr/bin/bash
+set -euo pipefail
+
+json_file="/var/lib/zabbix/telemt-active-ips.json"
+metrics_file="/var/lib/zabbix/telemt-metrics.prom"
+
+case "${1:-}" in
+  active_ips_count)
+    jq '[.users[].active_unique_ips[]] | unique | length' "${json_file}"
+    ;;
+  connections_current)
+    awk '$1 ~ /^telemt_user_connections_current\{/ {sum += $2} END {print sum + 0}' "${metrics_file}"
+    ;;
+  connections_total)
+    awk '$1 ~ /^telemt_user_connections_total\{/ {sum += $2} END {print sum + 0}' "${metrics_file}"
+    ;;
+  bytes_received)
+    awk '$1 ~ /^telemt_user_octets_from_client\{/ {sum += $2} END {printf "%.0f\n", sum + 0}' "${metrics_file}"
+    ;;
+  bytes_sent)
+    awk '$1 ~ /^telemt_user_octets_to_client\{/ {sum += $2} END {printf "%.0f\n", sum + 0}' "${metrics_file}"
+    ;;
+  uptime)
+    awk '$1 == "telemt_uptime_seconds" {printf "%.0f\n", $2; found=1} END {if (!found) exit 1}' "${metrics_file}"
+    ;;
+  *)
+    printf 'unsupported Telemt value: %s\n' "${1:-}" >&2
+    exit 2
+    ;;
+esac