feat(jobs): 提交后回填补偿落库 backfill_todo 并到期重试 (ACM2-29 P2-3)

- V1.3.2 迁移：backfill_todo 持久补偿表（attempts/next_attempt_at/last_error）
- BackfillTodoRepository 接口 + PG 实现与 stub；record 幂等 upsert
- BackfillSweepJob：到期重试，成功即删，失败指数退避（30s 起步封顶 15 分钟）；
  触发点 = InboxPoller 每轮心跳（重启即对账）+ JobExecutor BACKFILL_SWEEP 类型
- MessageProcessor/SnapshotFlow 回填失败落待办（成功终态不降级，业务不重放）；
  SKIPPED 重复报文同样补偿共享信箱回填，防止重复信件被反复轮询
- 新测试：扫描重试/退避/恢复对账 4 用例；快照回填失败落库断言；
  跳过路径补偿落库断言

验证：MSGX_PG_PORT=5433 真实 PG 全量 102 用例 0 失败 0 跳过 (ACM2-29)

src/main/kotlin/com/gzzn/omms/msgexchange/ingress/InboxPoller.kt

@@ -2,6 +2,7 @@ package com.gzzn.omms.msgexchange.ingress
 
 import com.gzzn.omms.msgexchange.config.PipelineProps
 import com.gzzn.omms.msgexchange.infra.persistence.CminmsgInboxRepository
+import com.gzzn.omms.msgexchange.jobs.BackfillSweepJob
 import jakarta.inject.Singleton
 
 /**
@@ -12,6 +13,7 @@ import jakarta.inject.Singleton
 class InboxPoller(
     private val inbox: CminmsgInboxRepository,
     private val enqueue: InboxEnqueue,
+    private val backfillSweep: BackfillSweepJob,
     private val props: PipelineProps,
 ) {
     private val log = org.slf4j.LoggerFactory.getLogger(InboxPoller::class.java)
@@ -30,9 +32,22 @@ class InboxPoller(
                 log.info("polled cminmsgsId={}", id)
             }
         }
+        sweepBackfillTodos()
         return enqueued
     }
 
+    /** v2 §5：每轮心跳顺带对账回填补偿待办（重启即恢复；空表只花一次索引 SELECT）。 */
+    private fun sweepBackfillTodos() {
+        try {
+            val outcome = backfillSweep.sweep()
+            if (outcome.inspected > 0) {
+                log.info("backfill sweep inspected={} succeeded={} failed={}", outcome.inspected, outcome.succeeded, outcome.failed)
+            }
+        } catch (e: Exception) {
+            log.error("backfill sweep tick failed", e)
+        }
+    }
+
     fun loop() {
         running = true
         log.info("inbox poller loop started")