Allow linking color palette to wallpaper selection

### Feature Description

This is a feature implemented in Noctalia and it makes managing theming much easier. It simply allows the user to link a specific palette to any wallpaper, so that when the wallpaper is selected, the corresponding theme palette is loaded also. This would much more efficient than selecting the wallpaper in the Wallpaper tab, then going to Settings, selecting Theme and Colors, and changing the Matugen pallete or custom palette to the preferred option. You could add palette selection options to the Wallpaper tab to make setting this up even easier.

### Use Case

I use Auto Dynamic Theming and usually the Matugen palette that works best for one wallpaper tends to look awful with another, so I end up having to go to Theme and Colors to select a new Matugen palette scheme each time I change wallpapers. Linking the preferred Matugen palette to each wallpaper on initial setup removes the need to constantly change Matugen palettes manually by restoring the correct palette each time the wallpaper is selected.

I assume the above could apply to Custom palettes as well, like using Catppuccin with one wallpaper and Tokyo Night with another.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

Expand the Wallpaper tab to incorporate Theme and Color options, so that the user can set the wallpaper, set the color theme (Matugen or Custom), and link them together, all in one interface.

### Alternatives/Existing Solutions

Check the Noctalia UI for comparison. They use a "favorites" like mechanism, where the user clicks a star for wallpapers where they want the current wallpaper/them combination to be remembered.