Use a single table instead of nested tables to better display column membership

### What feature do you want to see added?

Since I have just looked at the current design due to a redesign PR in the current release, I noticed again that the readability is currently somewhat suboptimal, as the table headings are not aligned with the cells.

For example, you might just think that Last Success and Last Failure were before 11h (i.e. that it is a combined cell). But Last Failure has the value "N/A":


Suggestion (Single table with indentation until job column):

Suggestion (Single table with indentation of all columns):

In the suggestion I removed the table (via Inspector, so I don't have a PR for this) and added to the "Status" and "Weather" cells a `margin-left: 40px` and to the job cell `margin-left: 15px` so that they have the same indentation as before, because I think that was there to make the sub-elements easier to see. Alternatively, you could, for example, slightly adjust the background of the category rows so that they stand out more without having to change the indentation (I don't know if other plugins often add columns or not, which you might have to consider).

### Upstream changes

_No response_

### Are you interested in contributing this feature?

_No response_

Start by locating the current Categorized Jobs View table rendering and its styling, then compare the existing layout with the supplied screenshots. The work is complete when column headings and cells are visibly aligned in a single table while category or sub-element indentation remains clear, or an equivalent category-row distinction is implemented.

Written by the indexing model from the issue text.