feat(app): 初始化自动关机工具首个版本

实现基于 WPF 的 AutoShutdown 主界面，支持关机、重启、睡眠、休眠、唤醒、锁屏和注销等电源任务。

支持指定时间和倒计时计划、执行前提醒、系统关机撤销、Windows 唤醒任务、托盘运行、自定义图标以及 OmniNotify 通知适配。

修复关闭到托盘时的运行提醒，并支持单击托盘图标打开或收起主界面。

补充 README、发布配置和 win-x64 Release 输出要求。

Release: win-x64

Services/NotificationService.cs

@@ -0,0 +1,92 @@
+using System.Net.Http;
+using System.Text;
+using System.Text.Json;
+using System.Windows;
+using AutoShutdown.Models;
+
+namespace AutoShutdown.Services;
+
+internal sealed class NotificationService
+{
+    private static readonly HttpClient HttpClient = new();
+
+    private NotificationSettings _settings;
+
+    public NotificationService(NotificationSettings settings)
+    {
+        _settings = settings;
+    }
+
+    public void UpdateSettings(NotificationSettings settings)
+    {
+        _settings = settings;
+    }
+
+    public async Task NotifyAsync(Window owner, string title, string body, MessageBoxImage image = MessageBoxImage.Information)
+    {
+        if (_settings.Mode == NotificationMode.OmniNotify)
+        {
+            await TrySendToOmniNotifyAsync(title, body);
+            return;
+        }
+
+        System.Windows.MessageBox.Show(owner, body, title, MessageBoxButton.OK, image);
+    }
+
+    public Task NotifyAsync(string title, string body)
+    {
+        return _settings.Mode == NotificationMode.OmniNotify
+            ? TrySendToOmniNotifyAsync(title, body)
+            : Task.CompletedTask;
+    }
+
+    public async Task<bool> TestOmniNotifyAsync(NotificationSettings settings)
+    {
+        var oldSettings = _settings;
+        try
+        {
+            _settings = settings;
+            await SendToOmniNotifyAsync("AutoShutdown 测试消息", "OmniNotify 适配已连接。");
+            return true;
+        }
+        catch
+        {
+            return false;
+        }
+        finally
+        {
+            _settings = oldSettings;
+        }
+    }
+
+    private async Task SendToOmniNotifyAsync(string title, string body)
+    {
+        if (!Uri.TryCreate(_settings.OmniNotifyEndpoint, UriKind.Absolute, out var endpoint))
+        {
+            return;
+        }
+
+        var payload = JsonSerializer.Serialize(new
+        {
+            channel = string.IsNullOrWhiteSpace(_settings.Channel) ? "default" : _settings.Channel.Trim(),
+            title,
+            body
+        });
+
+        using var content = new StringContent(payload, Encoding.UTF8, "application/json");
+        using var response = await HttpClient.PostAsync(endpoint, content);
+        response.EnsureSuccessStatusCode();
+    }
+
+    private async Task TrySendToOmniNotifyAsync(string title, string body)
+    {
+        try
+        {
+            await SendToOmniNotifyAsync(title, body);
+        }
+        catch
+        {
+            // OmniNotify 适配模式下不再弹窗打扰用户，发送失败只静默跳过。
+        }
+    }
+}