修复主题切换持久化问题

- 新增 UiPreferencesService 服务用于管理UI配置
- 主题选择自动保存到 appsettings.local.json
- 刷新页面后自动恢复用户的主题偏好
- 无需额外的设置选项，点击切换按钮即可

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/TelegramPanel.Web/Components/Layout/MainLayout.razor

@@ -26,6 +26,9 @@
     </MudMainContent>
 </MudLayout>
 
+@using TelegramPanel.Web.Services
+@inject UiPreferencesService UiPreferences
+
 @code {
     private bool _drawerOpen = true;
     private bool _isDarkMode = true;
@@ -48,13 +51,21 @@
         }
     };
 
+    protected override async Task OnInitializedAsync()
+    {
+        // 从配置文件读取用户的主题偏好
+        _isDarkMode = await UiPreferences.GetIsDarkModeAsync();
+    }
+
     private void ToggleDrawer()
     {
         _drawerOpen = !_drawerOpen;
     }
 
-    private void ToggleDarkMode()
+    private async Task ToggleDarkMode()
     {
         _isDarkMode = !_isDarkMode;
+        // 保存主题偏好到配置文件
+        await UiPreferences.SetIsDarkModeAsync(_isDarkMode);
     }
 }

src/TelegramPanel.Web/Program.cs

@@ -291,6 +291,7 @@ builder.Services.AddTelegramPanelData(connectionString);
 builder.Services.AddTelegramPanelCore();
 builder.Services.AddScoped<AccountExportService>();
 builder.Services.AddScoped<DataSyncService>();
+builder.Services.AddScoped<UiPreferencesService>();
 builder.Services.AddHostedService<BatchTaskBackgroundService>();
 builder.Services.AddHostedService<AccountDataAutoSyncBackgroundService>();
 builder.Services.AddHostedService<BotAutoSyncBackgroundService>();

src/TelegramPanel.Web/Services/UiPreferencesService.cs

@@ -0,0 +1,90 @@
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using Microsoft.AspNetCore.Hosting;
+
+namespace TelegramPanel.Web.Services;
+
+/// <summary>
+/// UI 偏好设置服务，用于管理用户界面相关的配置（如主题模式）
+/// </summary>
+public class UiPreferencesService
+{
+    private readonly IConfiguration _configuration;
+    private readonly IWebHostEnvironment _environment;
+    private readonly string _configFilePath;
+    private readonly SemaphoreSlim _writeLock = new(1, 1);
+
+    public UiPreferencesService(IConfiguration configuration, IWebHostEnvironment environment)
+    {
+        _configuration = configuration;
+        _environment = environment;
+        _configFilePath = LocalConfigFile.ResolvePath(configuration, environment);
+    }
+
+    /// <summary>
+    /// 获取当前的深色模式设置
+    /// </summary>
+    public async Task<bool> GetIsDarkModeAsync()
+    {
+        try
+        {
+            if (!File.Exists(_configFilePath))
+                return true; // 默认使用深色模式
+
+            var json = await File.ReadAllTextAsync(_configFilePath);
+            var doc = JsonDocument.Parse(json);
+
+            if (doc.RootElement.TryGetProperty("UI", out var uiSection) &&
+                uiSection.TryGetProperty("IsDarkMode", out var isDarkModeValue))
+            {
+                return isDarkModeValue.GetBoolean();
+            }
+
+            return true; // 默认使用深色模式
+        }
+        catch
+        {
+            return true; // 出错时默认使用深色模式
+        }
+    }
+
+    /// <summary>
+    /// 设置深色模式
+    /// </summary>
+    public async Task SetIsDarkModeAsync(bool isDarkMode)
+    {
+        await _writeLock.WaitAsync();
+        try
+        {
+            // 确保配置文件存在
+            await LocalConfigFile.EnsureExistsAsync(_configFilePath);
+
+            // 读取现有配置
+            var json = await File.ReadAllTextAsync(_configFilePath);
+            var jsonObj = JsonNode.Parse(json)?.AsObject() ?? new JsonObject();
+
+            // 更新 UI 配置
+            if (!jsonObj.ContainsKey("UI"))
+            {
+                jsonObj["UI"] = new JsonObject();
+            }
+
+            var uiSection = jsonObj["UI"]!.AsObject();
+            uiSection["IsDarkMode"] = isDarkMode;
+
+            // 写入配置文件
+            var options = new JsonSerializerOptions
+            {
+                WriteIndented = true,
+                Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
+            };
+            var updatedJson = JsonSerializer.Serialize(jsonObj, options);
+            await LocalConfigFile.WriteJsonAtomicallyAsync(_configFilePath, updatedJson);
+        }
+        finally
+        {
+            _writeLock.Release();
+        }
+    }
+}