Fornax: COORDINATOR_URL env, port-lease webhook, Grafana dashboard

- Worker deployment: add COORDINATOR_URL and WORKER_ID env vars to
  portforward-helper; webhook calls coordinator /api/v2/workers/:id/port-lease
  after each NAT-PMP renewal so coordinator tracks current forwarded port
- Worker overlays: patch WORKER_ID env var to actual worker ID (tx253/tx34)
- Grafana: fornax-grafana Argo CD app pointing to k8s/fornax/grafana/
  ConfigMap with grafana_dashboard=1 label for auto-discovery by sidecar;
  7 panels covering bandwidth, active torrents, worker health, request rate,
  and error rate

servers/legion/apps/fornax.yaml

@@ -63,3 +63,25 @@ spec:
       selfHeal: true
     syncOptions:
       - CreateNamespace=true
+---
+# Fornax Grafana dashboard — auto-discovered by Grafana sidecar (grafana_dashboard=1)
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: fornax-grafana
+  namespace: argocd
+spec:
+  project: default
+  source:
+    repoURL: http://10.43.1.53:3000/will/infrastructure.git
+    targetRevision: main
+    path: servers/legion/k8s/fornax/grafana
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: monitoring
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+      - CreateNamespace=true