fix css variables not updating correctly when system theme changes

resources/js/utils/useCssVariable.ts

@@ -0,0 +1,49 @@
+import { ref, onMounted, onUnmounted } from 'vue'
+
+export function useCssVariable(variableName: string) {
+  const value = ref('')
+  let observer: MutationObserver | null = null
+  let mediaQuery: MediaQueryList | null = null
+  
+  const updateValue = () => {
+    const computedStyle = getComputedStyle(document.documentElement)
+    const cssValue = computedStyle.getPropertyValue(variableName).trim()
+    value.value = cssValue
+  }
+  
+  onMounted(() => {
+    // Initialize with current value
+    updateValue()
+    
+    // Watch for class changes on document.documentElement (where theme classes are applied)
+    observer = new MutationObserver((mutations) => {
+      mutations.forEach((mutation) => {
+        if (mutation.type === 'attributes' && mutation.attributeName === 'class') {
+          updateValue()
+        }
+      })
+    })
+    
+    observer.observe(document.documentElement, {
+      attributes: true,
+      attributeFilter: ['class']
+    })
+    
+    // Also watch for system color scheme changes
+    if (window.matchMedia) {
+      mediaQuery = window.matchMedia('(prefers-color-scheme: dark)')
+      mediaQuery.addEventListener('change', updateValue)
+    }
+  })
+  
+  onUnmounted(() => {
+    if (observer) {
+      observer.disconnect()
+    }
+    if (mediaQuery) {
+      mediaQuery.removeEventListener('change', updateValue)
+    }
+  })
+  
+  return value
+}