General small plot improvements and website organisation

[jwarner8]

1. Add watermark with min/mean/max to plot - currently not user configurable to keep GUI simple.
2. Increase number of contour levels to 20 from 10, to see more granularity in variables.
3. Improve categorisation of recipes, as "Quick Looks" becomes quickly difficult to navigate through with large workflows.
4. Relax restriction of ylim on histogram plots (previously 0 to 1), which made some plots illegible if x values are large (like pressure) as it is a normalised PDF where the area under the curve is equal to 1.
5. Additional variables in default colorbar json and some tweaks to defaults. Recognise users will want different ranges depending on regions/seasons, but hopefully changes to defaults/additions here a useful starting point.

Contribution checklist

Aim to have all relevant checks ticked off before merging. See the developer's guide for more detail.

• Documentation has been updated to reflect change.
• New code has tests, and affected old tests have been updated.
• All tests and CI checks pass.
• Ensured the pull request title is descriptive.
• Conda lock files have been updated if dependencies have changed.
• Attributed any Generative AI, such as GitHub Copilot, used in this PR.
• Marked the PR as ready to review.

[github-actions]

[jfrost-mo]

Some really nice additions. Left a couple small comments, so just ping me for re-review after they are addressed. This is mostly to remind me to port the changes over to the pcolormesh plots.

[jfrost-mo]

Looks good. Just use the script to sort the colour bar file, then merge.