Feature Request: Dark mode for Web UI

### Checklist

- [X] This is **not** a question or a support request. If you have any boost related questions, please ask in the [discussion forum](https://github.com/filecoin-project/boost/discussions).
- [X] This is **not** a new feature or enhancement request. If it is, please open a [new idea discussion](https://github.com/filecoin-project/boost/discussions/new?category=ideas) instead. New feature and enhancement requests would be entertained by the boost team after a thorough discussion only.
- [X] I **have** searched on the [issue tracker](https://github.com/filecoin-project/boost/issues) and the [discussion forum](https://github.com/filecoin-project/boost/discussions), and there is no existing related issue or discussion.
- [X] I am running the [`Latest release`](https://github.com/filecoin-project/boost/releases), or the most recent RC(release canadiate) for the upcoming release or the dev branch(master), or have an issue updating to any of these.
- [X] I did not make any code changes to boost.

### Boost component

- [ ] boost daemon - storage providers
- [ ] boost client
- [X] boost UI
- [ ] boost data-transfer
- [ ] boost index-provider
- [X] Other

### Boost Version

```text
boostd version 1.4.0-rc1+git.e5b59d2
```

### Describe the Bug

Every Boost user at night right now:

### Logging Information

```text
Not needed.
```

### Repo Steps

- Open the Web UI at 01:00am

The issue names only the Boost Web UI and does not identify files, tests, or a frontend technology. Start by opening the Web UI and locating its entry point and styling files, then define the dark-mode coverage and verify it visually. Done means the Web UI has a usable dark appearance.

Written by the indexing model from the issue text.