Migrate k8s config from Terraform to Argo CD + ESO

Phase 1: Install External Secrets Operator via Argo CD app
- apps/external-secrets.yaml — ESO Helm chart install
- apps/external-secrets-config.yaml — ClusterSecretStore deployment
- k8s/external-secrets/cluster-secret-store.yaml — Vault backend using vault-token Secret

Phase 2: Create k8s manifests for all services
- k8s/neuron/ — PVC, ConfigMap, ExternalSecrets (neuron-secrets, cloudflared-secret), Ingress
- k8s/gitea/ — PVC, ConfigMap (custom CSS), ExternalSecret (gitea-db), Ingress
- k8s/github-runner/ — ExternalSecret (github-runner-secret)
- k8s/gitea-runner/ — ExternalSecret (gitea-runner-secret)
- k8s/monitoring/ — ExternalSecrets (grafana, slack), Alloy OTLP service+middleware, datasources ConfigMap, Ingress
- k8s/postgres/ — ExternalSecret (postgres-passwords)
- k8s/vault/ — ExternalSecret (vault-gcp-sa from Vault)
- k8s/adguard/ — PVCs, ConfigMap, Certificate, Ingress, ddclient Deployment+ExternalSecret
- k8s/ollama/ — PVC, Ingress
- k8s/headscale/ — PVC
- k8s/packages/ — PVCs, ConfigMap, Ingresses
- k8s/registry/ — PVC, Ingresses
- k8s/backup/ — CronJob, ExternalSecret (backup-credentials)

New Argo CD apps for Helm releases:
- apps/kube-prometheus-stack.yaml, loki.yaml, tempo.yaml, alloy.yaml
- apps/postgres.yaml, redis.yaml, vault.yaml

New Argo CD apps for k8s config paths:
- apps/neuron-config, gitea-config, ci-config, gitea-runner-config
- apps/monitoring-config, adguard-config, ollama-config, headscale-config
- apps/packages-config, registry-config, postgres-config, vault-config, backup

Phase 3: Strip Terraform to infrastructure-only
- All kubernetes_* and helm_release resources removed from service .tf files
- Each service .tf now contains only kubernetes_namespace (bootstrap dependency)
- variables.tf stripped to only cloudflare_api_key, cloudflare_email, gitea_api_token
- namespaces.tf gains external-secrets namespace
- ingress.tf, backup.tf, ddclient.tf emptied (resources in k8s/)
- cert-manager.tf, argocd.tf, traefik.tf unchanged (bootstrap)

servers/legion/postgres.tf

@@ -1,34 +1,3 @@
-# Shared Postgres — Kong, app databases
-resource "helm_release" "postgres" {
-  name       = "postgres"
-  namespace  = kubernetes_namespace.platform.metadata[0].name
-  repository = "oci://registry-1.docker.io/bitnamicharts"
-  chart      = "postgresql"
-
-  timeout = 600
-
-  set {
-    name  = "auth.postgresPassword"
-    value = var.postgres_password
-  }
-
-  set {
-    name  = "primary.persistence.size"
-    value = "20Gi"
-  }
-
-  set {
-    name  = "primary.resources.requests.memory"
-    value = "256Mi"
-  }
-
-  set {
-    name  = "primary.resources.requests.cpu"
-    value = "100m"
-  }
-
-  set {
-    name  = "primary.initdb.scripts.create-kong-db\\.sql"
-    value = "CREATE DATABASE kong; CREATE USER kong WITH PASSWORD '${var.kong_db_password}'; GRANT ALL PRIVILEGES ON DATABASE kong TO kong; ALTER DATABASE kong OWNER TO kong;"
-  }
-}
+# Shared Postgres — namespace only
+# Helm release and secrets managed by Argo CD + ESO
+# See: apps/postgres.yaml, apps/postgres-config.yaml, k8s/postgres/