fix: normalize Proxmox endpoint and stop dashboards self-trigger

Accept Proxmox API endpoints with or without /api2/json in CI and local
tfvars, and avoid running the dashboards workflow just because its own
workflow file changed during platform migrations.

terraform/main.tf

@@ -14,8 +14,15 @@ terraform {
   }
 }
 
+locals {
+  proxmox_endpoint_normalized = format(
+    "%s/",
+    trimsuffix(replace(trimspace(var.proxmox_endpoint), "/api2/json", ""), "/")
+  )
+}
+
 provider "proxmox" {
-  endpoint  = var.proxmox_endpoint
+  endpoint  = local.proxmox_endpoint_normalized
   api_token = "${var.proxmox_api_token_id}=${var.proxmox_api_token_secret}"
   insecure  = var.proxmox_insecure
 }