docs(kms): document /keys.json carve-out + script auto-key selection

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

stacks/blog/.terraform.lock.hcl

@@ -87,3 +87,11 @@ provider "registry.terraform.io/hashicorp/vault" {
     "zh:ff35fb1ab6add288f0f368981e56f780b50405accd1937131cba1137999c8d83",
   ]
 }
+
+provider "registry.terraform.io/telmate/proxmox" {
+  version     = "3.0.2-rc07"
+  constraints = "3.0.2-rc07"
+  hashes = [
+    "h1:zp5hpQJQ4t4zROSLqdltVpBO+Riy9VugtfFbpyTw1aM=",
+  ]
+}

stacks/blog/providers.tf

@@ -20,6 +20,10 @@ terraform {
       source  = "gavinbunney/kubectl"
       version = "~> 1.14"
     }
+    proxmox = {
+      source  = "telmate/proxmox"
+      version = "3.0.2-rc07"
+    }
   }
 }