Ask the user to deploy, and explain how

Once the Expert has written the flows, they sit on the canvas doing nothing until the user deploys. So the Expert has to ask, and the ask has to work for someone who has never seen a Node-RED editor before and doesn't know what Deploy means.

That's the whole task: prompt for it, and describe how well enough that an unfamiliar user can act on it. Where the button is, what pressing it does, what they should expect to happen after.

### Done when

* The Expert asks the user to deploy once the flows are written.
* The description is enough for someone who has never used Node-RED to find the button and understand what it does.
* It doesn't ask when the flows came from a blueprint and are already running.

### Worth knowing

Work lands in the flows on `expert-api-dev`, not this repo.

Deploy is a Node-RED control inside its own editor, so there's nothing on the FlowFuse side to hook into. No highlighting the button, no driving it from the platform. Describing it well is the whole lever we have.

This is deliberate rather than a gap. Deploy means immediate execution of whatever is on the canvas, so the user reviewing and pressing it themselves is the security boundary. Worth saying so in plain terms in the message: the Expert built it, they take a look and set it running. That frames the ask as them being in control rather than the Expert being unable.

Wording carries a lot here. "Press Deploy" assumes they already know what deploying is and why they'd want to. Something closer to what it does for them will land better, and it's worth trying a few phrasings on someone unfamiliar rather than settling on the first.

flowfuse#8323 is relevant: the Expert can start writing before the immersive editor has finished loading. If that's still open when this is picked up, the deploy ask could arrive before the canvas has settled.