chore: bump Node.js version to 22 across CI, docs, and package manifest

docs/SETUP.md

@@ -5,7 +5,7 @@ This guide covers prerequisites, environment setup, running the application loca
 ## Prerequisites
 
 - **Docker & Docker Compose**: Required for running the full stack (playout, chat, nginx, redis, db, prometheus, grafana). Install from [docker.com](https://www.docker.com).
-- **Node.js 20+**: Required for frontend development and production builds (`cd frontend && npm install && npm run build`).
+- **Node.js 22+**: Required for frontend development and production builds (`cd frontend && npm install && npm run build`).
 - **npm**: Installed with Node.js and used for the frontend dependency installation and Vite workflow.
 - **Go 1.23+**: Recommended when working on the Go services outside Docker (`backend/chat`, `backend/playout`).
 - **FFmpeg**: Used by the playout service for HLS generation. Install via `apt install ffmpeg` (Linux), Homebrew (macOS), or Winget (Windows).