Add docker availability check to all scripts that use docker commands

22 scripts used docker without verifying it's present. Consistent with the
pattern already established in Docker_Essentials scripts. Added after acquire_lock
and before detect_hosts in each script's setup section.

Orchestrators/array_stopping.sh

@@ -60,6 +60,11 @@ validate_unraid_cmd \
 
 acquire_lock
 
+if ! command -v docker &>/dev/null; then
+    error "Docker command not found"
+    exit 1
+fi
+
 detect_hosts
 
 [[ "$DRY_RUN" == true ]] && warn "DRY RUN — no stop scripts will be executed"