feat: enhance background layer handling and uploader functionality

- Introduced automatic overlay opacity and gradient based on layer ID in BackgroundLayer component.
- Added disabled state to BackgroundUploader, preventing actions when disabled.
- Updated component CSS editor to handle disabled state, preventing changes when disabled.
- Modified Header and Layout components to manage background inheritance from the page layer.
- Improved Sidebar and Card components to respect background inheritance and layering.
- Refactored theme management to include default accent color and normalization functions.
- Enhanced AppearanceTab to manage accent color changes with debouncing and validation.
- Added UI feedback for inherited background layers in AppearanceTab.

dashboard/src/hooks/use-background.ts

@@ -5,13 +5,19 @@ import { defaultBackgroundConfig } from '@/lib/theme/tokens'
 
 type BackgroundLayerId = 'page' | 'sidebar' | 'header' | 'card' | 'dialog'
 
+type ResolvedBackgroundState = {
+  config: BackgroundConfig
+  inheritEnabled: boolean
+  inheritedFrom: BackgroundLayerId | null
+}
+
 /**
  * 获取指定层级的背景配置
  * 处理继承逻辑：如果 inherit 为 true，返回页面级别配置
  * @param layerId - 背景层级标识
  * @returns 对应层级的背景配置
  */
-export function useBackground(layerId: BackgroundLayerId): BackgroundConfig {
+export function useBackground(layerId: BackgroundLayerId): ResolvedBackgroundState {
   const { themeConfig } = useTheme()
   const bgMap = themeConfig.backgroundConfig ?? {}
 
@@ -19,8 +25,16 @@ export function useBackground(layerId: BackgroundLayerId): BackgroundConfig {
 
   // 处理继承逻辑：非 page 层级且 inherit 为 true，返回 page 配置
   if (layerId !== 'page' && config.inherit) {
-    return bgMap.page ?? defaultBackgroundConfig
+    return {
+      config: bgMap.page ?? defaultBackgroundConfig,
+      inheritEnabled: true,
+      inheritedFrom: 'page',
+    }
   }
 
-  return config
+  return {
+    config,
+    inheritEnabled: !!config.inherit,
+    inheritedFrom: null,
+  }
 }