wire soul to web_demo_key for Anthropic API isolation

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

@@ -8,7 +8,7 @@
 # routes still go to the Cloud Run prod URL until we cut over.
 #
 # Vault paths used:
-#   secret/neuron-technologies/anthropic        api_key
+#   secret/neuron-technologies/anthropic        api_key, web_demo_key
 #   secret/neuron-technologies/supabase         anon_key, service_role_key, project_url
 #   secret/neuron-technologies/marketing-test   stripe_*, etc.
 #   secret/neuron-technologies/notifications    resend_api_key
@@ -38,7 +38,7 @@ spec:
     - secretKey: NEURON_LLM_0_KEY
       remoteRef:
         key: secret/data/neuron-technologies/anthropic
-        property: api_key
+        property: web_demo_key
     - secretKey: SUPABASE_ANON_KEY
       remoteRef:
         key: secret/data/neuron-technologies/supabase