fix(picker): update transparent color handling for light and dark modes

Author: betavs

src/common/style/theme/_components.less

@@ -1,10 +1,15 @@
 // 部分特殊处理的组件级 token
 @media (prefers-color-scheme: light) {
+  page,
+  .page {
+    --td-transparent-color: rgba(255, 255, 255, 0);
+  }
 }
 
 @media (prefers-color-scheme: dark) {
   page,
   .page {
+    --td-transparent-color: transparent;
     --td-button-primary-disabled-color: var(--td-font-white-4);
     --td-skeleton-animation-gradient: rgba(255, 255, 255, 6%);
     --td-slider-dot-bg-color: var(--td-gray-color-4);

src/picker/picker.less

@@ -85,12 +85,12 @@
 
     &--top {
       top: 0;
-      background: linear-gradient(180deg, @picker-bg-color 0%, transparent 100%);
+      background: linear-gradient(180deg, @picker-bg-color 0%, var(--td-transparent-color) 100%);
     }
 
     &--bottom {
       bottom: 0;
-      background: linear-gradient(180deg, @picker-bg-color 0%, transparent 100%);
+      background: linear-gradient(180deg, @picker-bg-color 0%, var(--td-transparent-color) 100%);
       transform: matrix(1, 0, 0, -1, 0, 0);
     }
   }