feat(server): /metrics 可观测与日志上下文（F22）

- 新增 Prometheus 指标端点 /metrics（HTTP + DB + 作业统计）
- request.log 绑定 requestId/actorId，避免日志难追踪
- cron/pg-boss 作业增加 metrics 计数（runs/processed）
- 更新 env/runbook/README 与 v3 CSV 状态推进

server/src/jobs/invoiceArchiveJob.js

@@ -76,12 +76,32 @@ function startInvoiceArchiveJob(fastify) {
 
     running = true;
     try {
-      await archiveUnusedInvoices(fastify.prisma, fastify.log, {
+      const archived = await archiveUnusedInvoices(fastify.prisma, fastify.log, {
         batchSize: fastify.config.invoiceArchiveBatchSize,
         unusedDays: fastify.config.invoiceArchiveUnusedDays,
       });
+      fastify.metrics?.jobRunsTotal?.inc?.({
+        job: "invoice.archive-unused",
+        driver: "cron",
+        outcome: "success",
+      });
+      if (archived > 0) {
+        fastify.metrics?.jobProcessedTotal?.inc?.(
+          {
+            job: "invoice.archive-unused",
+            driver: "cron",
+            kind: "archived",
+          },
+          archived,
+        );
+      }
     } catch (error) {
       fastify.log.error({ err: error }, "Invoice archive job failed");
+      fastify.metrics?.jobRunsTotal?.inc?.({
+        job: "invoice.archive-unused",
+        driver: "cron",
+        outcome: "failure",
+      });
     } finally {
       running = false;
     }
@@ -107,4 +127,3 @@ module.exports = {
   archiveUnusedInvoices,
   startInvoiceArchiveJob,
 };
-