feat: add tracing enrichment and prometheus exporter

Document/05_部署运维.md

@@ -709,35 +709,37 @@ scrape_configs:
       - targets: ['node-exporter:9100']
 ```
 
-### 8.2 应用监控指标
+### 8.2 应用监控指标（OpenTelemetry + Prometheus Exporter）
 ```csharp
-// Program.cs - 添加Prometheus监控
-builder.Services.AddPrometheusMetrics();
+// Program.cs - 指标与探针
+builder.Services.AddHealthChecks();
+builder.Services.AddOpenTelemetry()
+    .WithMetrics(metrics =>
+    {
+        metrics
+            .AddAspNetCoreInstrumentation()
+            .AddHttpClientInstrumentation()
+            .AddRuntimeInstrumentation()
+            .AddPrometheusExporter(); // /metrics
+    });
 
-app.UseMetricServer(); // /metrics端点
-app.UseHttpMetrics(); // HTTP请求指标
+var app = builder.Build();
+app.MapHealthChecks("/healthz");          // 存活/就绪探针
+app.MapPrometheusScrapingEndpoint();      // 默认 /metrics
+```
 
-// 自定义指标
-public class MetricsService
+自定义业务指标（使用 `System.Diagnostics.Metrics`，由 Prometheus Exporter 暴露）：
+```csharp
+internal static class BusinessMetrics
 {
-    private static readonly Counter OrderCreatedCounter = Metrics
-        .CreateCounter("orders_created_total", "Total orders created");
-
-    private static readonly Histogram OrderProcessingDuration = Metrics
-        .CreateHistogram("order_processing_duration_seconds", "Order processing duration");
-
-    public void RecordOrderCreated()
-    {
-        OrderCreatedCounter.Inc();
-    }
-
-    public IDisposable MeasureOrderProcessing()
-    {
-        return OrderProcessingDuration.NewTimer();
-    }
+    private static readonly Meter Meter = new("TakeoutSaaS.App", "1.0.0");
+    public static readonly Counter<long> OrdersCreated = Meter.CreateCounter<long>("orders_created_total", "个", "订单创建计数");
+    public static readonly Histogram<double> OrderProcessingSeconds = Meter.CreateHistogram<double>("order_processing_duration_seconds", "s", "订单处理耗时");
 }
 ```
 
+Prometheus 抓取示例：见 `deploy/prometheus/prometheus.yml`，默认拉取 `/metrics`，告警规则见 `deploy/prometheus/alert.rules.yml`。
+
 ### 8.3 Grafana仪表板
 ```json
 {
@@ -1007,4 +1009,3 @@ docker-compose up -d --force-recreate --no-deps api
 docker pull takeout-saas-api:previous-version
 docker-compose up -d
 ```
-