Update website overall design

[Yndira-E]

Description

In pursuit of a more professional appearance that aligns with the brand attributes outlined in this document, and taking into consideration our design inspiration websites, we'll implement layout and color scheme changes to the website..

### Tasks
- [ ] https://github.com/FlowFuse/website/issues/1672
- [ ] https://github.com/FlowFuse/website/issues/1656
- [ ] https://github.com/FlowFuse/website/issues/1693
- [ ] https://github.com/FlowFuse/website/issues/1655
- [ ] https://github.com/FlowFuse/website/issues/1750
- [ ] https://github.com/FlowFuse/website/issues/1753

[Yndira-E]

Next steps: review all pages and iterate on them