Display in-app release highlights after each update

### Epic

_No response_

### Description

**As a:**
FlowFuse user who regularly works with the platform

**I want to:**
See a short summary of what’s new in the latest release (feature highlights, improvements, etc.) when I log in

**So that:**
I can quickly understand what’s changed or improved, stay informed without having to check external sources, and make use of new features right away

Currently, we share release updates through blog posts, social media, and newsletters, but they’re easily missed or forgotten shortly after the announcement. This proposal aims to keep users engaged with product updates by surfacing highlights in-app on login—similar to the way Adobe Premiere Pro presents “What’s New” using a modal. (see image below).

This could include:

- A short video or animated gif demoing a major feature
- 2–3 key bullet points from the release
- A link to the full changelog on flowfuse.com

For new signups, we should keep the current product tour as-is. Then, when a new version is released, we can show the “What’s New” screen only to returning users.

### Which customers would this be available to

None

### Acceptance Criteria

- [ ] criteria 1
- [ ] criteria 2
- [ ] criteria 3
- ...

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

I have provided an initial effort estimate