feat(calendar): simplify holiday highlight styles and improve accessibility

- Introduced a new visual style for holiday highlights in the calendar component, replacing complex gradients with solid colors for better clarity.
- Removed the holiday badge to reduce visual noise and enhance user experience.
- Ensured that holiday information remains accessible through long-press interactions.
- Updated specifications to reflect the new design decisions and requirements for both light and dark themes.
- Added tasks for implementation, including style adjustments and accessibility enhancements.

Web/src/assets/theme.css

@@ -79,6 +79,10 @@
   
   /* 边框颜色 */
   --border-color: #E5E7EB;
+
+  /* 分段控制器 (Segmented Control) - From .pans/v2.pen NDWwE */
+  --segmented-bg: #F4F4F5;
+  --segmented-active-bg: #FFFFFF;
 }
 
 /* ============ 深色主题 ============ */
@@ -110,6 +114,10 @@
   /* 图标色 (深色主题) */
   --icon-star: #FF6B6B;
   --icon-coffee: #FCD34D;
+
+  /* 分段控制器 (Segmented Control) - From .pans/v2.pen NDWwE */
+  --segmented-bg: #27272a;
+  --segmented-active-bg: #3f3f46;
 }
 
 /* ============ 通用工具类 ============ */