security: remove all REDACTED secrets from repo, add pre-commit guard

- Delete 26 secret manifests containing REDACTED placeholder values
  (15 cert-manager TLS + 11 app secrets across 8 namespaces)
- REDACTED is valid base64 that decodes to non-UTF-8 bytes — ArgoCD
  applying these manifests corrupts live secrets in the cluster
- Add .githooks/pre-commit that rejects any .yaml with REDACTED
- Add README.md documenting secret management policy and manual
  creation commands for each service
- n8n secret manifests already fixed in previous commits (618b1e8, db04fd2)

authentik/secret-auth-tls.yaml

@@ -1,21 +0,0 @@
-apiVersion: v1
-data:
-  tls.crt: REDACTED
-  tls.key: REDACTED
-kind: Secret
-metadata:
-  annotations:
-    cert-manager.io/alt-names: auth.chemavx.xyz
-    cert-manager.io/certificate-name: auth-tls
-    cert-manager.io/common-name: auth.chemavx.xyz
-    cert-manager.io/ip-sans: ''
-    cert-manager.io/issuer-group: cert-manager.io
-    cert-manager.io/issuer-kind: ClusterIssuer
-    cert-manager.io/issuer-name: letsencrypt-prod
-    cert-manager.io/uri-sans: ''
-  labels:
-    controller.cert-manager.io/fao: 'true'
-  name: auth-tls
-  namespace: authentik
-type: kubernetes.io/tls
-

authentik/secret-authentik-secrets.yaml

@@ -1,15 +0,0 @@
-apiVersion: v1
-data:
-  AUTHENTIK_POSTGRESQL__PASSWORD: REDACTED
-  AUTHENTIK_SECRET_KEY: REDACTED
-  POSTGRES_PASSWORD: REDACTED
-kind: Secret
-metadata:
-  annotations:
-    kubectl.kubernetes.io/last-applied-configuration: '{"apiVersion":"v1","kind":"Secret","metadata":{"annotations":{},"name":"authentik-secrets","namespace":"authentik"},"stringData":{"AUTHENTIK_POSTGRESQL__PASSWORD":"authentik","AUTHENTIK_SECRET_KEY":"PLACEHOLDER_WILL_UPDATE","POSTGRES_PASSWORD":"authentik"},"type":"Opaque"}
-
-      '
-  name: authentik-secrets
-  namespace: authentik
-type: Opaque
-

authentik/secret-authentik-tls.yaml

@@ -1,21 +0,0 @@
-apiVersion: v1
-data:
-  tls.crt: REDACTED
-  tls.key: REDACTED
-kind: Secret
-metadata:
-  annotations:
-    cert-manager.io/alt-names: authentik.chemavx.xyz
-    cert-manager.io/certificate-name: authentik-tls
-    cert-manager.io/common-name: authentik.chemavx.xyz
-    cert-manager.io/ip-sans: ''
-    cert-manager.io/issuer-group: cert-manager.io
-    cert-manager.io/issuer-kind: ClusterIssuer
-    cert-manager.io/issuer-name: letsencrypt-prod
-    cert-manager.io/uri-sans: ''
-  labels:
-    controller.cert-manager.io/fao: 'true'
-  name: authentik-tls
-  namespace: authentik
-type: kubernetes.io/tls
-