1. What you need

Three tools, installed once:

• Node.js 24.15.0 or newer on the Node 24 line, or Node 26 and later. Node runs the JavaScript code of both halves of the app, and it comes with npm, the tool that installs the app's libraries. Check your version with node -v. The accepted range is the engines field in backend/package.json and frontend/package.json; npm only warns when you are outside it, so check it yourself.
• Docker, with Docker Compose (the docker compose command, included in current Docker installs). Docker runs the database and the local mail inbox in containers, small isolated environments, so you do not install them yourself. Check with docker compose version.
• Git, to get the code and save your changes. Check with git --version.

You also need a code editor and your AI coding agent. Nothing else is required for local development: no accounts, no keys, no paid services.

Next: Get the code and install