Harden prod: security, autoscaling, observability, BuildKit CI

Security:
- Drop ALL capabilities, enforce non-root, RuntimeDefault seccomp on
  neuron-mcp, neuron-rest, neuron-marketing pods
- Add startup probes (150s window for JVM) so liveness doesn't fire early
- Replace docker-sock hostPath with BuildKit rootless TCP endpoint
  (moby/buildkit:v0.19.0-rootless) — removes node root access from CI
- Document full ESO AppRole migration path in cluster-secret-store.yaml

Autoscaling & availability:
- HPAs on mcp (1–6), rest (1–4), marketing (2–8) at 65–70% CPU
- PodDisruptionBudgets (minAvailable: 1) on all three services
- NetworkPolicy: default-deny-all in neuron-prod, explicit allow rules
  for Traefik ingress, intra-namespace, and egress to DNS/platform/vault

Observability:
- ServiceMonitors for mcp, rest, marketing (cross-namespace enabled in
  kube-prometheus-stack with serviceMonitorSelectorNilUsesHelmValues:false)
- PrometheusRules: high error rate, high latency, crash loops, replica
  shortage, Postgres down/connections, backup failure, backup staleness

Chart version pinning:
- kube-prometheus-stack, loki, tempo, redis, alloy, postgres — all pinned
  to major-version ranges to block silent breaking upgrades

Backup hardening:
- restic:latest → restic:0.17.3 (deterministic image)
- Weekly backup-verify CronJob: restores latest snapshot and validates
  SQL dump structure (≥5 CREATE TABLE, pg_dump header check)

ArgoCD:
- neuron-prod AppProject: scopes deploys to neuron-prod + platform ns,
  blacklists ClusterRole/ClusterRoleBinding/Namespace creation,
  automated sync window 2–6am UTC, manual always allowed

servers/legion/k8s/neuron-technologies/marketing/deployment.yaml

@@ -17,6 +17,11 @@ spec:
         app: neuron-marketing
         env: prod
     spec:
+      securityContext:
+        runAsNonRoot: true
+        runAsUser: 1001
+        seccompProfile:
+          type: RuntimeDefault
       containers:
         - name: neuron-marketing
           image: registry.neuralplatform.ai/neuron-technologies/marketing:1e94e8ae
@@ -24,6 +29,12 @@ spec:
           ports:
             - name: http
               containerPort: 3000
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: false  # Next.js writes .next/cache at runtime
+            runAsNonRoot: true
+            capabilities:
+              drop: ["ALL"]
           env:
             - name: NODE_ENV
               value: production