fix: resolve current episode highlight color and focus clash (#499)

- Prioritize active focus highlights over the next-up episode card border.
- Style the next-up episode border using AppColorScheme.onSurface (cyan in Neon Pulse, white in Moonfin) with a thicker width of 2.5.
- Update preference migration keys in unit tests from v1 to v2 to align with main branch implementation.

Co-authored-by: mattsigal <mattsigal@users.noreply.github.com>

Author: mattsigal

lib/ui/screens/detail/item_detail_screen.dart

@@ -9044,18 +9044,18 @@ class _EpisodeListCardState extends State<_EpisodeListCard>
             width: widget.isMobile ? 180.0 : 220.0 * desktopScale,
             decoration: BoxDecoration(
               borderRadius: BorderRadius.circular(8),
-              border: widget.isCurrent
+              border: showFocusBorder
                   ? Border.fromBorderSide(
                       ThemeRegistry.active.borders.focusBorder.copyWith(
-                        color: AppColorScheme.accent,
-                        width: 2,
+                        color: isNeon ? AppColorScheme.accent : focusColor,
+                        width: 1.5,
                       ),
                     )
-                  : showFocusBorder
+                  : widget.isCurrent
                   ? Border.fromBorderSide(
                       ThemeRegistry.active.borders.focusBorder.copyWith(
-                        color: isNeon ? AppColorScheme.accent : focusColor,
-                        width: 1.5,
+                        color: AppColorScheme.onSurface,
+                        width: 2.5,
                       ),
                     )
                   : null,