update-apps: follow renamed ct/ scripts instead of erroring out

A container keeps the slug it was built with, so a renamed ct/ script leaves
the updater looking for a name that no longer exists.

Reported for pbs, renamed to proxmox-backup-server in 0e5f663df. The Alpine
merge on 2026-08-18 retired 29 more names the same way, so every container
installed from an alpine-* script before that date hits this too.

Candidates are only accepted when the target script really exists, so an
unknown slug still errors rather than running some other app's updater.

Fixes #16989

tools/pve/update-apps.sh

@@ -155,13 +155,29 @@ function sanitize_service_name() {
   return 0
 }
 
-function validate_service_script() {
+function script_exists() {
   local name="$1"
   sanitize_service_name "$name" || return 1
   curl -fsSL --max-time 10 -o /dev/null \
     "https://raw.githubusercontent.com/community-scripts/ProxmoxVE/main/ct/${name}.sh" 2>/dev/null
 }
 
+# A container keeps the slug it was built with, so a renamed ct/ script leaves it
+# pointing at a name that no longer exists. Try the successors, but only accept one
+# that is really there -- guessing wrong would run a foreign app's updater.
+function resolve_service_script() {
+  local n="$1" c
+  script_exists "$n" && { printf '%s' "$n"; return 0; }
+  for c in "${n#alpine-}" "$(printf '%s' "$n" | sed -E 's/-v[0-9]+$//')"; do
+    [[ -n "$c" && "$c" != "$n" ]] || continue
+    script_exists "$c" && { printf '%s' "$c"; return 0; }
+  done
+  case "$n" in
+  pbs) script_exists proxmox-backup-server && { printf '%s' proxmox-backup-server; return 0; } ;;
+  esac
+  return 1
+}
+
 function detect_service() {
   local container="$1"
   local tmpdir update_file
@@ -484,12 +500,18 @@ for container in $CHOICE; do
     continue
   fi
 
-  if ! validate_service_script "${service}"; then
+  resolved_service="$(resolve_service_script "${service}")"
+  if [ -z "${resolved_service}" ]; then
     echo -e "${RD}[ERROR]${CL} Service '${service}' does not resolve to ct/${service}.sh"
     log_result "$container" "${service}" "ERROR" "No matching ct/${service}.sh script found"
     log_write "Container $container: ERROR — ct/${service}.sh not found"
     continue
   fi
+  if [ "${resolved_service}" != "${service}" ]; then
+    echo -e "${BL}[INFO]${CL} Script was renamed: ${service} -> ${GN}${resolved_service}${CL}"
+    log_write "Container $container: slug ${service} resolved to ${resolved_service}"
+    service="${resolved_service}"
+  fi
 
   echo -e "${BL}[INFO]${CL} Detected service: ${GN}${service}${CL}"
   log_write "Container $container: detected service '${service}'"