feat: 优化主题切换逻辑，添加浅色主题支持，更新相关样式

src/composables/useTheme.ts

@@ -1,5 +1,3 @@
-import { usePreferredDark } from "@vueuse/core";
-
 export type ThemeMode = "light" | "dark" | "auto";
 
 const STORAGE_KEY = "app-theme-mode";
@@ -16,7 +14,14 @@ export function useTheme() {
   });
 
   watch(isDark, (dark) => {
-    document.documentElement.classList.toggle("ion-palette-dark", dark);
+    if (dark) {
+      document.documentElement.classList.toggle("ion-palette-dark", dark);
+      document.documentElement.classList.remove("ion-palette-light");
+    }
+    else {
+      document.documentElement.classList.remove("ion-palette-dark");
+      document.documentElement.classList.add("ion-palette-light");
+    }
   }, { immediate: true });
 
   return {