Sorting by release date in descending order shows dates in ascending order (icon ↑ shown for descending, ↓ shown for ascending)

[Ryziii]

Bug: When sorting items (audiobooks/episodes) by release date in descending order (newest first), the actual order displayed is ascending (oldest first).

Root cause: The chevron icon mapping for sort direction is inverted in ItemSortOrderPicker.icon(for:), which misleads users into selecting the wrong direction.

In App/Item/Picker/ItemSortOrderPicker.swift:28 (and two other locations):

// Current (wrong):
ascending ? "chevron.down" : "chevron.up"

Apple's convention is chevron.up = ascending (A→Z, oldest→newest), chevron.down = descending (Z→A, newest→oldest). Because the mapping is backwards, when ascending is false (descending), the UI shows chevron.up (↑). Users interpret ↑ as ascending, think the sort is oldest-first, and toggle — which actually switches to ascending, making dates oldest-first when they expect newest-first.

Affected files:

App/Item/Picker/ItemSortOrderPicker.swift:28
App/Panels/AudiobookTagsPanel.swift:52
App/Panels/AudiobookGenresPanel.swift:52

Fix:

ascending ? "chevron.up" : "chevron.down"

Note: The ascending Bool itself is used correctly everywhere else (API desc param, local sort logic, persistence) — only the icon mapping is wrong.