add neuron-web phase-1 deploy on Legion

Stand up the elb-built native El landing server on Legion k3s alongside
the existing Cloud Run prod marketing site. Image is built on
gitea-runner-1 from elb-emitted .c files + native cc and pushed to
registry.neuralplatform.ai/neuron-web:dev-dfe41234. Deployment exposes
web-stage.neuralplatform.ai via Traefik + Cloudflare tunnel.

The point is to have a working local instance we can iterate against
while we redesign the CI/CD pipeline; nothing here replaces the Cloud
Run deploy yet.

* k8s/neuron-technologies/web/ — namespace, deployment, service, ingress,
  registry-pull-secret + externalsecret pulling anthropic/supabase keys
  from Vault
* apps/neuron-web.yaml — Argo CD Application
* dns-neuralplatform.tf, main.tf — CNAME + tunnel ingress for
  web-stage.neuralplatform.ai

servers/legion/k8s/neuron-technologies/web/ingress.yaml

@@ -0,0 +1,25 @@
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: neuron-web
+  namespace: neuron-web
+  annotations:
+    traefik.ingress.kubernetes.io/router.entrypoints: websecure
+    cert-manager.io/cluster-issuer: letsencrypt-prod
+spec:
+  ingressClassName: traefik
+  tls:
+    - hosts:
+        - web-stage.neuralplatform.ai
+      secretName: neuron-web-tls
+  rules:
+    - host: web-stage.neuralplatform.ai
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: neuron-web
+                port:
+                  number: 8080