feat(monitoring): surveillance réseau active via blackbox_exporter

Sondes actives ICMP/HTTP/DNS qui complètent le monitoring passif
(node_exporter + up{}) : joignabilité hôtes/passerelle, accès internet,
santé DNS *.lab.local + forwarding, latence LAN, services de bout en
bout via Traefik.

- blackbox_exporter (chart 11.13.0, ArgoCD, ns monitoring) — ICMP via
  NET_RAW, DNS du pod = dnsmasq (chemin réel lab → Traefik)
- 3 jobs blackbox-icmp/-http/-dns (additionalScrapeConfigs)
- alerts-network.yaml : internet, DNS, passerelle, hôtes, services,
  latence, exporter (→ pipeline AlertManager existant)
- Asa : outil network_status + contexte présélectionnable reseau
- doc admin/infra/reseau.md + CLAUDE.md + progress

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rc3dLKfqEPHexvFCCx5ZEF

k8s/apps-of-apps/apps/blackbox-exporter.yaml

@@ -0,0 +1,29 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: blackbox-exporter
+  namespace: argocd
+  finalizers:
+    - resources-finalizer.argocd.argoproj.io
+spec:
+  project: default
+  sources:
+    - repoURL: https://prometheus-community.github.io/helm-charts
+      chart: prometheus-blackbox-exporter
+      targetRevision: 11.13.0
+      helm:
+        valueFiles:
+          - $values/k8s/infra/blackbox-exporter/values.yaml
+    - repoURL: git@github.com:Alkatrazz24/Funk-lab.git
+      targetRevision: main
+      ref: values
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: monitoring
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+      - CreateNamespace=true
+      - ServerSideApply=true