[web] Transparent bug path points are distractingly see-through and hard to focus

[whisperity]

Is your feature request related to a problem? Please describe.
At some point in time the behaviour of the web UI was changed s.t. bug note points that are not the currently selected one are see-through. While there are ways to change which note is in focus, they are clunky.

1. You can move the mouse to the left-side tree view (assuming it's wide enough that you can read it...) and click on another bug point.
2. You can click on the arrows in any bubble, to jump to the previous/next of the bubble.

Describe the solution you would like
There is no way to select any arbitrary bubble to be the current, focused one, without tracking down its number in the tree view, or tracking down the directly preceding/following bubble and using the arrows there. However, my mouse and my attention are already where I am currently focusing! I wanted to "save" this information while I navigate to some other window for arbitrary reading, but I can't, because instead I am forced to remember a number.

Bubbles should respond to normal clicks and by clicking on a bubble, focus should move there. (Including both the visual effect and the selection row in the tree view!) Currently, the click does nothing.

The transparency is too obstructive! See the following examples. Due to the lack of contrast between the underlaid bright arrow and the bubble itself, even if I could manage remembering the bug point's number, I can't see what number it is...

At the very least, the transparency value should either be user-configurable, or if this is hard to do, a toggle for whether the transparency is used should be added. There already is a toggle for the arrows.

Note that there are guidelines for accessibility such as here: https://www.w3.org/WAI/WCAG22/Understanding/contrast-minimum.html.