style: adjust button background colors for better visual consistency

Updated button background color definitions in FlowStyle.qml to improve
visual consistency across different themes and states. Changed crystal
theme colors to use simplified RGBA values (0,0,0 instead of 16/255) for
better maintainability. Added missing hoveredDark and pressedDark states
for crystal theme to ensure proper dark mode support. Adjusted opacity
values for better contrast and visual hierarchy in both light and dark
themes.

Log: Improved button visual appearance in different themes

style: 调整按钮背景颜色以提升视觉一致性

更新了 FlowStyle.qml 中的按钮背景颜色定义，以改善不同主题和状态下的视觉
一致性。将水晶主题颜色改为使用简化的 RGBA 值（0,0,0 替代 16/255）以提高
可维护性。为水晶主题添加了缺失的 hoveredDark 和 pressedDark 状态，确保正
确的深色模式支持。调整了透明度值以在浅色和深色主题中获得更好的对比度和视
觉层次。

Log: 改进了不同主题下按钮的视觉外观

PMS: BUG-268509 BUG-327451

Author: mhduiy

qt6/src/qml/FlowStyle.qml

@@ -108,15 +108,23 @@ QtObject {
             }
             normalDark {
                 common: Qt.rgba(1, 1, 1, 0.1)
-                crystal: Qt.rgba(1, 1, 1, 0.1)
+                crystal: Qt.rgba(1, 1, 1, 0.08)
             }
             hovered {
                 common: ("#e1e1e1")
-                crystal:  Qt.rgba(16.0 / 255, 16.0 / 255, 16.0 / 255, 0.2)
+                crystal:  Qt.rgba(0, 0, 0, 0.2)
+            }
+            hoveredDark {
+                common:  Qt.rgba(1, 1, 1, 0.2)
+                crystal:  Qt.rgba(1, 1, 1, 0.2)
             }
             pressed {
                 common: ("#bcc4d0")
-                crystal: Qt.rgba(16.0 / 255, 16.0 / 255, 16.0 / 255, 0.15)
+                crystal: Qt.rgba(0, 0, 0, 0.15)
+            }
+            pressedDark {
+                common:  Qt.rgba(1, 1, 1, 0.05)
+                crystal:  Qt.rgba(1, 1, 1, 0.05)
             }
         }
 
@@ -207,21 +215,23 @@ QtObject {
             }
             normalDark {
                 common: D.DTK.makeColor(D.Color.Highlight).saturation(+10).lightness(+10)
-                crystal: Qt.rgba(0, 0, 0, 0.1)
+                crystal: Qt.rgba(1, 1, 1, 0.08)
             }
             hovered {
                 common: D.DTK.makeColor(D.Color.Highlight).lightness(+10).saturation(+20).lightness(+10)
-                crystal: Qt.rgba(16.0 / 255, 16.0 / 255, 16.0 / 255, 0.2)
+                crystal: Qt.rgba(0, 0, 0, 0.2)
             }
             hoveredDark {
                 common: D.DTK.makeColor(D.Color.Highlight).lightness(+10).saturation(+30).lightness(+10)
+                crystal: Qt.rgba(1, 1, 1, 0.2)
             }
             pressed {
                 common: D.DTK.makeColor(D.Color.Highlight).lightness(-10).saturation(+8).lightness(-8)
                 crystal: Qt.rgba(16.0 / 255, 16.0 / 255, 16.0 / 255, 0.15)
             }
             pressedDark {
                 common: D.DTK.makeColor(D.Color.Highlight).saturation(+10).lightness(+2)
+                crystal: Qt.rgba(1, 1, 1, 0.05)
             }
             disabled {
                 common: D.DTK.makeColor(D.Color.Highlight).saturation(+22).lightness(+14)