[monitoring] Opt-out external monitor for family/mladost3/task-webhook/torrserver; drop r730

The `external-monitor-sync` script is opt-IN by default for any
*.viktorbarzin.me ingress, so a missing annotation means "monitored."
Both ingress factories previously OMITTED the annotation when
`external_monitor = false`, which silently left monitors in place.

Fix: when the caller sets `external_monitor = false` explicitly, emit
`uptime.viktorbarzin.me/external-monitor = "false"` so the sync script
deletes the monitor. Keep the previous behavior (no annotation) for
callers that leave external_monitor null — otherwise 19 publicly-reachable
services with `dns_type="none"` would lose monitoring.

Set external_monitor=false on family (grampsweb) and mladost3 (reverse-proxy)
to match the other two already-flagged services. Delete the r730 ingress
module entirely — the Dell server has been decommissioned.

stacks/reverse-proxy/modules/reverse_proxy/main.tf

@@ -151,25 +151,6 @@ module "truenas" {
   depends_on = [kubernetes_namespace.reverse-proxy]
 }
 
-# https://r730.viktorbarzin.me/
-module "r730" {
-  source           = "./factory"
-  name             = "r730"
-  external_name    = "r730.viktorbarzin.lan"
-  port             = 443
-  tls_secret_name  = var.tls_secret_name
-  backend_protocol = "HTTPS"
-  depends_on       = [kubernetes_namespace.reverse-proxy]
-  extra_annotations = {
-    "gethomepage.dev/enabled"      = "true"
-    "gethomepage.dev/name"         = "R730"
-    "gethomepage.dev/description"  = "Dell PowerEdge server"
-    "gethomepage.dev/icon"         = "dell.png"
-    "gethomepage.dev/group"        = "Infrastructure"
-    "gethomepage.dev/pod-selector" = ""
-  }
-}
-
 # https://proxmox.viktorbarzin.me/
 module "proxmox" {
   source           = "./factory"
@@ -268,6 +249,7 @@ module "mladost3" {
   port              = 8080
   tls_secret_name   = var.tls_secret_name
   depends_on        = [kubernetes_namespace.reverse-proxy]
+  external_monitor  = false
   extra_annotations = { "gethomepage.dev/enabled" = "false" }
 }