Inconsistent 'Up Next' Dark Theme Behavior for Chapter Lists

### Description

The `Chapters`' background remains in light mode while "Use Dark Up Next Theme" is active.

This is for an unplayed episode in the Up Next list.

Reported in https://forums.pocketcasts.com/forums/topic/appearance-use-dark-up-next-theme/?view=all#post-6838

Some key points:

> The phone is currently in the light theme and I set the default light theme in the App and turned Use Android Light/Dark Mode on.

> When I choose the “Dark” theme under appearance settings, tapping an episode on the Up Next page correctly displays a dark background for its Chapter list. However, if I switch the theme to Light, Rose, or Indigo with “Use Dark Up Next Theme” enabled, the Chapter list’s background turns white instead of remaining dark as intended.

> Given that tapping an episode on the Up Next page results in dark background for Details and Bookmarks when this option enabled, it would be consistent to apply the dark theme to the chapter list as well.

### Step-by-step reproduction instructions

1. Select "Light" under Profile > Settings > Appearance > Theme
2. Make sure "Use Dark Up Next Theme" is selected
3. Add an episode that has Chapters to Up Next
4. Play the episode to ensure the Chapters tab is shown
5. Play another episode to keep the said episode in the Up Next
6. Tap the episode, then view and compare the Details, Chapters, and Bookmarks tab
7. Observe the Chapters' background remains in light mode

Note: Ensure the episode is in an unplayed episode in the Up Next. The currently played episode will show the correctly dark background.

### Screenshots or screen recording


### Did you search for existing bug reports?

- [x] I have searched for existing bug reports.

### Device, Operating system, and Pocket Casts app version

Meizu 17, Android 13, Pocket Casts 7.76 (9282)

Also reproduced on Redmi Note 9 Pro, Android 12 (MIUI 14.0.1), Pocket Casts 7.77 (9286)

Start by reproducing the issue through Profile > Settings > Appearance > Theme, then compare the Details, Chapters, and Bookmarks tabs for an unplayed Up Next episode. The change is done when the Chapters tab keeps the dark background whenever “Use Dark Up Next Theme” is enabled, matching the other tabs.

Written by the indexing model from the issue text.