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/ocrJob.js

@@ -301,6 +301,29 @@ function startOcrJob(fastify) {
     running = true;
     try {
       const result = await runOcrOnce(fastify.prisma, fastify.config, fastify.log, workerId);
+      fastify.metrics?.jobRunsTotal?.inc?.({
+        job: "ocr.tick",
+        driver: "cron",
+        outcome: "success",
+      });
+      if (result.available > 0) {
+        fastify.metrics?.jobProcessedTotal?.inc?.(
+          { job: "ocr.tick", driver: "cron", kind: "available" },
+          result.available,
+        );
+      }
+      if (result.duplicate > 0) {
+        fastify.metrics?.jobProcessedTotal?.inc?.(
+          { job: "ocr.tick", driver: "cron", kind: "duplicate" },
+          result.duplicate,
+        );
+      }
+      if (result.failed > 0) {
+        fastify.metrics?.jobProcessedTotal?.inc?.(
+          { job: "ocr.tick", driver: "cron", kind: "failed" },
+          result.failed,
+        );
+      }
       if (result.claimed > 0) {
         fastify.log.info(
           {
@@ -312,6 +335,11 @@ function startOcrJob(fastify) {
       }
     } catch (error) {
       fastify.log.error({ err: error }, "OCR job tick failed");
+      fastify.metrics?.jobRunsTotal?.inc?.({
+        job: "ocr.tick",
+        driver: "cron",
+        outcome: "failure",
+      });
     } finally {
       running = false;
     }