fix(ingress): wire up backend_protocol, remove dead ssl_redirect variable

Post nginx→Traefik migration cleanup:
- backend_protocol now sets serversscheme + serverstransport annotations
  for HTTPS backends (k8s-dashboard, pfsense, nas, idrac, proxmox, etc.)
- Remove ssl_redirect variable (nginx-only, silently ignored by Traefik)
  and all 9 caller references

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stacks/nvidia/modules/nvidia/main.tf

@@ -208,7 +208,6 @@ module "ingress" {
   root_domain             = "viktorbarzin.lan"
   tls_secret_name         = var.tls_secret_name
   allow_local_access_only = true
-  ssl_redirect            = false
 }
 
 # resource "kubernetes_ingress_v1" "nvidia-exporter" {