monitoring02: enable alerting and migrate CNAMEs from http-proxy

- Switch vmalert from blackhole mode to sending alerts to local
  Alertmanager
- Import alerttonotify service so alerts route to NATS notifications
- Move alertmanager and grafana CNAMEs from http-proxy to monitoring02
- Add monitoring CNAME to monitoring02
- Add Caddy reverse proxy entries for alertmanager and grafana
- Remove prometheus, alertmanager, and grafana Caddy entries from
  http-proxy (now served directly by monitoring02)
- Move monitoring02 Vault AppRole to hosts-generated.tf with
  extra_policies support and prometheus-metrics policy
- Update Promtail to use authenticated loki.home.2rjus.net endpoint
  only (remove unauthenticated monitoring01 client)
- Update pipe-to-loki and bootstrap to use loki.home.2rjus.net with
  basic auth from Vault secret
- Move migration plan to completed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

system/pipe-to-loki.nix

@@ -16,7 +16,8 @@ let
     text = ''
       set -euo pipefail
 
-      LOKI_URL="http://monitoring01.home.2rjus.net:3100/loki/api/v1/push"
+      LOKI_URL="https://loki.home.2rjus.net/loki/api/v1/push"
+      LOKI_AUTH_FILE="/run/secrets/promtail-loki-auth"
       HOSTNAME=$(hostname)
       SESSION_ID=""
       RECORD_MODE=false
@@ -69,7 +70,13 @@ let
             }]
           }')
 
+        local auth_args=()
+        if [[ -f "$LOKI_AUTH_FILE" ]]; then
+          auth_args=(-u "promtail:$(cat "$LOKI_AUTH_FILE")")
+        fi
+
         if curl -s -X POST "$LOKI_URL" \
+          "''${auth_args[@]}" \
           -H "Content-Type: application/json" \
           -d "$payload" > /dev/null; then
           return 0