"Deploy to FlowFuse" Button

### Description

For a snapshot or Flow.json it would be great if there was a "Deploy to FlowFuse" button to allow faster deployment to FlowFuse.

Things to consider
- Integration with FlowViewer
- Putting this button on flows.nodered.org

Greg edit June 5 2025:
Raising this issue again to scope the work needed to create an instance from a snapshot or flow.json. The blueprint work is already completed.

Edit July 7 2025:
- Could add "Import from Flow.json" to Add Instance workflow alongside the Blueprint import area.

```[tasklist]
### First Iteration - Deploy Blueprint to FlowFuse
- [x] https://github.com/FlowFuse/flowfuse/issues/3946
```

```[tasklist]
### Second Iteration - Deploy _any_ flow to FlowFuse
- [ ] Accept `flow.json` into create instance form in some way
```

### Which customers would this be available to

None