remove SOPS pipeline, deploy ESO + Vault DB/K8s engines

Vault is now the sole source of truth for secrets. SOPS pipeline
removed entirely — auth via `vault login -method=oidc`.

Part A: SOPS removal
- vault/main.tf: delete 990 lines (93 vars + 43 KV write resources),
  add self-read data source for OIDC creds from secret/vault
- terragrunt.hcl: remove SOPS var loading, vault_root_token, check_secrets hook
- scripts/tg: remove SOPS decryption, keep -auto-approve logic
- .woodpecker/default.yml: replace SOPS with Vault K8s auth via curl
- Delete secrets.sops.json, .sops.yaml

Part B: External Secrets Operator
- New stack stacks/external-secrets/ with Helm chart + 2 ClusterSecretStores
  (vault-kv for KV v2, vault-database for DB engine)

Part C: Database secrets engine (in vault/main.tf)
- MySQL + PostgreSQL connections with static role rotation (24h)
- 6 MySQL roles (speedtest, wrongmove, codimd, nextcloud, shlink, grafana)
- 6 PostgreSQL roles (trading, health, linkwarden, affine, woodpecker, claude_memory)

Part D: Kubernetes secrets engine (in vault/main.tf)
- RBAC for Vault SA to manage K8s tokens
- Roles: dashboard-admin, ci-deployer, openclaw, local-admin
- New scripts/vault-kubeconfig helper for dynamic kubeconfig

K8s auth method with scoped policies for CI, ESO, OpenClaw, Woodpecker sync.

stacks/nextcloud/.terraform.lock.hcl

@@ -38,3 +38,23 @@ provider "registry.terraform.io/hashicorp/kubernetes" {
     "zh:f569b65999264a9416862bca5cd2a6177d94ccb0424f3a4ef424428912b9cb3c",
   ]
 }
+
+provider "registry.terraform.io/hashicorp/vault" {
+  version     = "4.8.0"
+  constraints = "~> 4.0"
+  hashes = [
+    "h1:GPfhH6dr1LY0foPBDYv9bEGifx7eSwYqFcEAOWOUxLk=",
+    "zh:269ab13433f67684012ae7e15876532b0312f5d0d2002a9cf9febb1279ce5ea6",
+    "zh:4babc95bf0c40eb85005db1dc2ca403c46be4a71dd3e409db3711a56f7a5ca0e",
+    "zh:78d5eefdd9e494defcb3c68d282b8f96630502cac21d1ea161f53cfe9bb483b3",
+    "zh:86e27c1c625ecc24446a11eeffc3ac319b36c2b4e51251db8579256a0dbcf136",
+    "zh:a32f31da94824009e26b077374440b52098aecb93c92ff55dc3d31dd37c4ea25",
+    "zh:be0a18c6c0425518bab4fbffd82078b82036a88503b5d76064de551c9f646cbf",
+    "zh:be5a77fdfd36863ebeec79cd12b1d13322ffad6821d157a0b279789fa06b5937",
+    "zh:be8317d142a3caad74c7d936039ae27076a1b2b8312ef5208e2871a5f525977c",
+    "zh:c94a84895a3d9954b80e983eed4603330a5cdbbd8eef5b3c99278c2d1402ef3c",
+    "zh:de1fb712784dd8415f011ca5346a34f87fab6046c730557615247e511dbc7d98",
+    "zh:e3eafae7da550f86cae395d6660b2a0e93ec8d2b0e0e5ef982ec762e961fc952",
+    "zh:ff35fb1ab6add288f0f368981e56f780b50405accd1937131cba1137999c8d83",
+  ]
+}

stacks/nextcloud/providers.tf

@@ -1,8 +1,22 @@
 # Generated by Terragrunt. Sig: nIlQXj57tbuaRZEa
+terraform {
+  required_providers {
+    vault = {
+      source  = "hashicorp/vault"
+      version = "~> 4.0"
+    }
+  }
+}
+
 variable "kube_config_path" {
   type    = string
   default = "~/.kube/config"
+}
+
+variable "vault_root_token" {
+  type      = string
   sensitive = true
+  default   = ""
 }
 
 provider "kubernetes" {
@@ -14,3 +28,9 @@ provider "helm" {
     config_path = var.kube_config_path
   }
 }
+
+provider "vault" {
+  address          = "https://vault.viktorbarzin.me"
+  token            = var.vault_root_token
+  skip_child_token = true
+}