Bump index.html content for local builds

[jekader]

When building locally, webui.py is not run so the resulting firmware contains outdated JS artifacts.

Bumping the version based on what the release PixelIt 2.5.0 firmware is serving as index.html

As a future improvement one of the following approaches can be used to ensure local builds get the correct index.html:

• add a github action to the WebUI repo which would create a PR similar to this one on each successful build. See here for an example.
• make webui.py run during each build stage and fetch a fresh index.html each time
• change index.html to fetch a fresh version from upstream and replace content (may be unsafe due to upgrading WebUI without upgrading the firmware)

[foorschtbar]

We already build a new "index.html" on each build, but use it only in the artefacts and dont repush it to the repo. Maybe a warning in the UI, that this is an outdated or static version or simething will helps? for testing a "old" ui is fine for me and when i change something on the UI, i use the UI Repo with the dev server.