Better sorting

[tkroening]

Description

Implements a new multi-sort UI and algorithm to allow sorting on an arbitrary combination of columns (and their biases and orderings) to address the need for sorting improvements.

Video demo

• The new "Multi-Sort" popup allows the user to build and edit a custom sort-order, and then have it applied on the "main page".
• The back-end has been updated with a new function that can sort based on a user-defined ordering of the columns. The original column sorting functionality has been left intact.

Fixes Kubis10#29

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a readme update

How Has This Been Tested?

This PR successfully implements the sort described in the original issue (Kubis10#29):

add option to sort by chat type and messages count in the same time

Test A

1. Load sample data
2. Click the "Multi-sort" button in the sidebar to open the new pop-up
3. To add the message type to the sort order: click "type" in "Available columns", click "Add", then click "Reverse" (to sort in descending order.
4. Do the same for the message count ("msg")
5. Click "Apply"

Result: the data is successfully sorted by chat type first, and message count second, both in descending order.

Test B

1. Load sample data
2. Click the "Multi-sort" button in the sidebar
3. Add just one column to the sort order, say "name"
4. Click "Apply"

Result: the data is successfully sorted by name

Test C

1. Load sample data
2. Click "name" column header

Result: the data is successfully sorted by name, as in the current version of the app.

Test Configuration:

• App version: 0.1.7 (with my changes added)
• Hardware: Framework Laptop 13 (Intel) running Debian Trixie

Checklist:

• My code follows the style guidelines of this project
  • Some small changes still remain (there is camelCase in some places)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
  • Not yet - this feature builds on a Linux fix I needed to add to run the app.

[tkroening]

New updates:

• Listboxes now display the full column titles and take up the full width of the window to accommodate them.
• The app initializes the multi-sort popup with the current sort ordering if it hasn't been cleared. The app clears the sort order if the user clicks on a column, but this behavior could be disabled with minimal changes.

Screenshot:

Video demo

[tkroening]

It may be helpful to merge this in so that people can work on top these changes more easily