New lightmode and darkmode themes with UI revamp.

[manyoso]

Describe your changes

Issue ticket number and link

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• I have added thorough documentation for my code.
• I have tagged PR with relevant project labels. I acknowledge that a PR without labels may be dismissed.
• If this PR addresses a bug, I have provided both a screenshot/video of the original bug and the working solution.

Demo

Steps to Reproduce

Notes

[cebtenzzre]

Could you explain why we are changing this?

[manyoso]

The application when it comes up is far smaller by default than other applications of its kind. Further, with the new home page we need more space for the large font and so on.

[cebtenzzre]

On my Mac, the links at the top neither light up nor change the cursor when you hover them, so it's not as obvious that they are clickable as it should be.

[manyoso]

On my Mac, the links at the top neither light up nor change the cursor when you hover them, so it's not as obvious that they are clickable as it should be.

Same behavior on linux. This is intended. I can change this, but not all links behave with something happening on hover.

[cebtenzzre]

And the smaller labels to the left of the controls are harder to read IMO:

Compared to the previous version:

Btw, you forgot to sign off on your commits, so the DCO check is failing. You should git commit --amend -s and force-push.

[cebtenzzre]

More small text on macOS:

[Phil209]

The new UI is hogging a 1080p monitor.

I often have a browser windows open docked on the right (or another app) and GPT4ALL docked on the left to look things up. But the new UI forces a very large minimal size so it doesn't docked to half of a 1920 wide screen, which is something I've never encountered before after using 100s of apps on a large 1920x1080 display.

Forcing a very large minimal window size is also making it harder to multi-task in other ways, such as watching a show while GPT4ALL is generating responses. Plus it messed up all my scripts I made to automate functionality. I would resize it to the same place so I could automate pasting, execution, copying... It's easy enough to re-write them to the new minimum size, but like I said, the new minimum size is far too large to allow multitasking on a 1920x1080 screen so I have to revert to the previous version.