Create 'what's new!' popup on first login after a release for SH and D

[gstout52]

Description

Follow on to this discussion: https://github.com/FlowFuse/flowfuse/issues/6207

For self-hosted and dedicated customers, when a new release is shipped, surface a notification that displays upon the first login and describes what is new in the release.

For a first iteration, a simple text summary that links to the release post is sufficient.

Epic/Story

No response

Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate

[ppawlowski]

@gstout52 Implementation of this task is beyond my area of expertise.