* fix(ui): allow DefaultTheme "Auto" from config
When DefaultTheme is set to "Auto" in the server config, the
defaultTheme() function in themeReducer now returns AUTO_THEME_ID
instead of falling through to the DarkTheme fallback.
This allows useCurrentTheme to correctly read prefers-color-scheme
and select Light or Dark theme automatically for new/incognito users.
Adds themeReducer unit tests covering Auto, named-theme, and
unrecognized-value fallback paths.
* chore: format
Signed-off-by: Deluan <deluan@navidrome.org>
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Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: Deluan <deluan@navidrome.org>
c42570446b