feat(ThemeProvider): keep auto value (#8068)

* refactor: 使用三元操作符兼容 net6

* refactor: 支持 auto 值

* refactor: bump version 10.6.5-beta01

Author: ArgoZhang

src/BootstrapBlazor/BootstrapBlazor.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Razor">
 
   <PropertyGroup>
-    <Version>10.6.4</Version>
+    <Version>10.6.5-beta01</Version>
   </PropertyGroup>
 
   <ItemGroup>

src/BootstrapBlazor/wwwroot/modules/utility.js

@@ -702,10 +702,7 @@ export function getTheme(useLocalstorage = true) {
         theme = document.documentElement.getAttribute('data-bs-theme');
     }
 
-    if (theme === null || theme === 'auto') {
-        theme = getAutoThemeValue();
-    }
-    return theme;
+    return theme == null ? 'auto' : theme;
 }
 
 export function saveTheme(theme) {
@@ -719,8 +716,8 @@ export function getAutoThemeValue() {
 }
 
 export function setTheme(theme, sync) {
-    if (theme === 'auto' && window.matchMedia('(prefers-color-scheme: dark)').matches) {
-        document.documentElement.setAttribute('data-bs-theme', 'dark')
+    if (theme === 'auto') {
+        document.documentElement.setAttribute('data-bs-theme', getAutoThemeValue())
     }
     else {
         document.documentElement.setAttribute('data-bs-theme', theme);