style: cool the sunset gradient base

The warm glow at the bottom of the dusk sky didn't fit — stay in the
blue range.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/aare/gui/styles.py

@@ -170,7 +170,7 @@ DARK_BACKGROUND_GRADIENT_MID = "#16294d"  # fade onset tone
 DARK_BACKGROUND_GRADIENT_MID_POS = "0.55"  # 0..1 — where the fade begins
 DARK_BACKGROUND_GRADIENT_BLUE = "#2c5f9e"  # the blue band
 DARK_BACKGROUND_GRADIENT_BLUE_POS = "0.90"  # 0..1 — warm glow only below this
-DARK_BACKGROUND_GRADIENT_BOTTOM = "#d9b98c"
+DARK_BACKGROUND_GRADIENT_BOTTOM = "#2c5f9e"  # the warm glow doesn't seem to fit
 DARK_APP_BACKGROUND = (
     "qlineargradient(x1:0, y1:0, x2:0, y2:1,"
     f" stop:0 {DARK_BACKGROUND_GRADIENT_TOP},"