Improve migration path to persistent storage

We have a number of FFC instances with the old template applied that excludes the file nodes. For those instances to make use of the file storage, they currently need to be updated by admin to remove the exclude.

This purpose of this issue is to improve that migration path; identify what we can do more proactively here.

We already warn the user if the file nodes are currently excluded in their template; but as we lock that setting they have to contact us for help.

**Proposal:** Instead show a button to enable the asset service for them - with a notice that doing so will restart their instance. A new backend API will be provided that automates the tasks (ensures launcher version compatibility, updates their project settings to remove file nodes). This will remove the need for them to contact us.

As a separate task, we should identify:

- how many active instances still have the file nodes excluded
- of those, how many are using the old file nodes/file server that need to migrate; we can proactively reach out to them to help them move over

Once we know the true scale of the matter, we can decide how much time is worth spending on it.