feat: add postgres/gitea/blackbox alerts and more node alerts

environments/dev/adibrov/alerts/nginx/nginx_high_connections.yaml

@@ -0,0 +1,19 @@
+name: "DEV ADIBROV - Nginx High Active Connections"
+expression: |
+  nginx_connections_active{job="nginx"}
+threshold: 500
+for: "5m"
+condition_type: "gt"
+need_reduce: true
+reducer_type: "max"
+no_data_state: "OK"
+exec_err_state: "Error"
+labels:
+  service: "nginx"
+  severity: "warning"
+  team: "infra"
+summary: |
+  Много активных соединений nginx: {{ $values.B.Value }} на {{ $labels.instance }}
+description: |
+  Количество активных соединений nginx на {{ $labels.instance }} превышает 500.
+  Возможна высокая нагрузка или атака.