Deploy Plane project management to k8s with Cloudflare Access gate

Adds all k8s manifests (namespace, postgres, redis, api, worker, beat,
web, ingress, externalsecret, configmap, kustomization), Argo CD Application,
and Cloudflare Zero Trust access policy for plane.neuralplatform.ai.

servers/legion/k8s/plane/externalsecret.yaml

@@ -0,0 +1,18 @@
+apiVersion: external-secrets.io/v1beta1
+kind: ExternalSecret
+metadata:
+  name: plane-secrets
+  namespace: plane
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    name: vault
+    kind: ClusterSecretStore
+  target:
+    name: plane-secrets
+    creationPolicy: Owner
+  data:
+    - secretKey: secret_key
+      remoteRef:
+        key: secret/data/plane/config
+        property: secret_key