Add portainer skill for stack management via API

- 11 scripts for stack lifecycle (start/stop/restart, update, prune)
- Detailed documentation with usage examples and workflow
- Updated README.md files with portainer skill info

skills/portainer/scripts/list-stacks.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+CONFIG_PATH="/home/node/.openclaw/workspace/.clawdbot/credentials/portainer/config.json"
+
+err() {
+  echo "Error: $*" >&2
+  exit 1
+}
+
+require_cmd() {
+  command -v "$1" >/dev/null 2>&1 || err "Required command not found: $1"
+}
+
+require_cmd curl
+require_cmd jq
+
+[[ -f "$CONFIG_PATH" ]] || err "Missing config file: $CONFIG_PATH"
+
+BASE_URL="$(jq -r '.base_url // empty' "$CONFIG_PATH")"
+API_KEY="$(jq -r '.api_key // empty' "$CONFIG_PATH")"
+
+[[ -n "$BASE_URL" ]] || err "config.base_url is missing"
+[[ -n "$API_KEY" ]] || err "config.api_key is missing"
+
+BASE_URL="${BASE_URL%/}"
+
+response="$(curl -sS -w $'\n%{http_code}' \
+  -H "X-API-Key: $API_KEY" \
+  "$BASE_URL/api/stacks")"
+
+http_code="$(printf '%s' "$response" | tail -n1)"
+body="$(printf '%s' "$response" | sed '$d')"
+
+if [[ "$http_code" -lt 200 || "$http_code" -ge 300 ]]; then
+  msg="$(printf '%s' "$body" | jq -r '.message // empty' 2>/dev/null || true)"
+  [[ -n "$msg" ]] || msg="$body"
+  err "Portainer API request failed (HTTP $http_code): $msg"
+fi
+
+printf '%s' "$body" | jq -r '.[] | "\(.Id)\t\(.Name)\t\(.Status)"'