报告XP.ReportEngine：新增 IReportService接口封装完整报告生成流程，支持外部类库直接调用；新增 ReportRequest、ReportServiceResult 请求/响应模型；新增引擎预热机制；PDF 生成改为 Task.Run 后台线程执行，解决进度窗口和主窗口卡死问题；完善文档。

XP.ReportEngine/Interfaces/IReportService.cs

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+using System.Threading.Tasks;
+using XP.ReportEngine.Models;
+
+namespace XP.ReportEngine.Interfaces
+{
+    /// <summary>
+    /// 报告服务接口（门面）| Report service interface (Facade)
+    /// 提供完整的报告生成流程，外部模块通过此接口调用报告功能
+    /// Provides complete report generation workflow for external modules
+    /// </summary>
+    /// <remarks>
+    /// 使用示例 | Usage example:
+    /// <code>
+    /// var request = new ReportRequest
+    /// {
+    ///     ProcessorOutputs = processorOutputs,
+    ///     Metadata = new ReportMetadata
+    ///     {
+    ///         SampleName = "PCB-001",
+    ///         OperatorName = "Operator",
+    ///         InspectionDate = DateTime.Now
+    ///     }
+    /// };
+    /// var result = await _reportService.GenerateAsync(request);
+    /// </code>
+    /// </remarks>
+    public interface IReportService
+    {
+        /// <summary>
+        /// 生成报告 | Generate report
+        /// 执行完整流程：生成报告ID → 数据适配 → 上下文组装 → 管线生成 → 文件保存
+        /// Executes full workflow: generate report ID → data adaptation → context assembly → pipeline generation → file saving
+        /// </summary>
+        /// <param name="request">报告生成请求 | Report generation request</param>
+        /// <returns>报告生成结果 | Report generation result</returns>
+        Task<ReportServiceResult> GenerateAsync(ReportRequest request);
+
+        /// <summary>
+        /// 预热报告引擎（建议在应用启动后台调用）| Warm up report engine (recommended to call in background on app startup)
+        /// 触发 iText7 初始化、字体加载、JIT 编译等一次性开销，避免首次生成报告时卡顿
+        /// Triggers iText7 initialization, font loading, JIT compilation to avoid first-run latency
+        /// </summary>
+        Task WarmUpAsync();
+    }
+}