add options in settings to vary "thickness of links" as well as "thickness of box highlight" of active node.

### Is there an existing issue for this?

- [x] I have searched the existing issues and checked the recent builds/commits

### What problem are you experiencing?

add options in settings to vary "thickness of links" as well as "thickness of box highlight" of active node. benefits obvious, i guess.

### When does this problem occur?

not a problem, a feature request

### How often do you encounter this problem?

Multiple times per day

### How much does this problem affect your workflow?

Blocks me from completing tasks

### Current workarounds

_No response_

### Ideas for solutions (Optional)

_No response_

### Additional context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-6681-add-options-in-settings-to-vary-thickness-of-links-as-well-as-thickness-of-box-high-2aa6d73d36508194bac2eab669f05c0c) by [Unito](https://www.unito.io)

No files, tests, or entry points are named in the issue. Start by locating the settings UI and the active-node, box-highlight, and link styling entry points; confirm how visual preferences are stored and applied. Done means settings independently control link thickness and active-node box-highlight thickness, with coverage for the resulting behavior.

Written by the indexing model from the issue text.