feat(delivery): 真实 Kafka 投递端口 + 闭合 G-BACKFILL-BACKOFF 配置缺口

- 新增 KafkaDeliveryPort：ProducerRegistry + 同步 Future.get() 至少一次投递，
  闭合 OPS-1 真实适配器要求与 US-07 INV-10/C-29
- 回填退避从硬编码 30s/15min 提升为 backfill-backoff-ms / backfill-backoff-cap-ms
  配置绑定，闭合 [G-BACKFILL-BACKOFF]
- 删除死依赖 micronaut-redis-lettuce（代码零引用，ACM2-28 Redis 已退出阶段 A）

src/main/kotlin/com/gzzn/omms/msgexchange/infra/kafka/KafkaDeliveryPort.kt

@@ -0,0 +1,46 @@
+package com.gzzn.omms.msgexchange.infra.kafka
+
+import com.gzzn.omms.msgexchange.delivery.DeliveryPort
+import io.micronaut.configuration.kafka.ProducerRegistry
+import io.micronaut.context.annotation.Requires
+import io.micronaut.core.type.Argument
+import jakarta.inject.Singleton
+import org.apache.kafka.clients.producer.Producer
+import org.apache.kafka.clients.producer.ProducerRecord
+
+/**
+ * Kafka 真实投递端口：通过 [ProducerRegistry] 拿 default 生产者，D3 参数
+ * （acks=all / enable-idempotence=true / max-in-flight=1）由 `KafkaD3Check` 启动自检。
+ *
+ * 发送同步等 broker 确认（`Future.get()`），语义是至少一次——满足 INV-10 / C-29。
+ * 仅在 `msgx.stubs != true` 时装配；stub 模式走 `StubDeliveryPort`。
+ */
+@Requires(property = "msgx.stubs", notEquals = "true")
+@Singleton
+class KafkaDeliveryPort(
+    private val registry: ProducerRegistry,
+) : DeliveryPort {
+
+    private val producer: Producer<String, String> by lazy {
+        registry.getProducer("default", Argument.of(String::class.java), Argument.of(String::class.java))
+    }
+
+    override fun sendKafka(topic: String, key: String, payloadJson: String) {
+        producer.send(ProducerRecord(topic, key, payloadJson)).get()
+    }
+
+    override fun sendKafkaSchd(topic: String, key: String, payloadJson: String) {
+        producer.send(ProducerRecord(topic, key, payloadJson)).get()
+    }
+
+    override fun sendKafkaNull(topic: String, key: String) {
+        producer.send(ProducerRecord<String, String>(topic, key, null)).get()
+    }
+
+    override fun ping(): Boolean = try {
+        producer.partitionsFor("msg")
+        true
+    } catch (_: Exception) {
+        false
+    }
+}