Revise product tour when shown on mobile devices.

### Epic

_No response_

### Description

**As a new FlowFuse Cloud user who signed up on a mobile device, I want a much simpler welcome message, so that I can more quickly and easily see the value in FlowFuse**

Our current product tour is the same whether a user is on a mobile device or a desktop, but the presentation of the product tour on mobile is very cluttered. Here is an example of how it looks:

https://eu.posthog.com/project/2209/replay/0197ab84-1773-71d6-ab9e-e8878e652df5?t=146

This is borne out in [our overall activation data](https://eu.posthog.com/project/2209/insights/iEN5L8rC), where users who sign up on mobile devices activate at 15 percentage points less than users on desktop (27% less, relatively).

A good first step in this direction would be to cut the product tour and instead provide a single welcome modal that simply greets the new user. After this modal, display the secondary "tour" that currently exists, which provides next-step documentation for users to get started.

### Which customers would this be available to

None

### Acceptance Criteria

- [ ] Revise the new user welcome for mobile users to be better conductive to the mobile view

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate