LeftFluent NavigationViewItem hover invisible in Light theme

[ACbye]

Describe the bug

Problem

When using NavigationView with PaneDisplayMode="LeftFluent" in Light theme,
the mouse hover background feedback is completely invisible.

Root Cause

NavigationViewItemBackgroundSelectedLeftFluent references ControlFillColorDefault,
which resolves to #B3FFFFFF (70% white semi-transparent) in Light theme.
Overlayed on the #FAFAFA application background:

State	Value	RGB
Background	#FAFAFA	(250, 250, 250)
+ Overlay	#B3FFFFFF	+70% white
Result	#FEFEFE	(254, 254, 254)
Delta		+4 ← imperceptible

Dark theme works correctly (+13), and Left/LeftMinimal modes work correctly
(they use SubtleFillColorSecondary for hover).

To Reproduce

N/A

Expected behavior

N/A

Screenshots

OS version

Windows 10 22H2 19045.7291

.NET version

.NET 8.0

WPF-UI NuGet version

4.3.0

Additional context

No response