fix: use PM_API_TOKEN_ID/SECRET env vars directly

- Remove token from Terraform variables (provider reads from env)
- Update workflows to set PM_API_TOKEN_ID and PM_API_TOKEN_SECRET directly
- Provider now reads credentials from environment variables

terraform/variables.tf

@@ -1,14 +1,3 @@
-variable "pm_api_token_id" {
-  type        = string
-  description = "Proxmox API token ID (format: user@realm!tokenid)"
-}
-
-variable "pm_api_token_secret" {
-  type        = string
-  sensitive   = true
-  description = "Proxmox API token secret"
-}
-
 variable "target_node" {
   type = string
 }