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

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

@@ -0,0 +1,19 @@
+name: "DEV ADIBROV - Nginx Down"
+expression: |
+  nginx_up{job="nginx"}
+threshold: 1
+for: "2m"
+condition_type: "lt"
+need_reduce: true
+reducer_type: "min"
+no_data_state: "Alerting"
+exec_err_state: "Alerting"
+labels:
+  service: "nginx"
+  severity: "critical"
+  team: "infra"
+summary: |
+  Nginx недоступен на {{ $labels.instance }}
+description: |
+  Nginx exporter не может подключиться к nginx на {{ $labels.instance }}.
+  Nginx либо упал, либо недоступен его status page.