chore(infra): 增加本地中间件编排、环境配置与 Kafka 降级支持

src/main/resources/application.yml

@@ -58,6 +58,7 @@ flyway:
 # （CminmsgMailbox/OutboxMailbox）随 U05 批次引入。
 mailbox:
   shared-mysql:
+    enabled: false
     url: ${MSGX_MAILBOX_URL}
     username: ${MSGX_MAILBOX_USER}
     password: ${MSGX_MAILBOX_PASSWORD}
@@ -71,9 +72,11 @@ kafka:
     servers: ${MSGX_KAFKA_SERVERS}
   producers:
     default:                        # U03/R09：Micronaut Kafka 按具名 producer 解析，须有 default 层
-      acks: all
-      enable-idempotence: true
-
+      # 默认 acks=all + 幂等（现代 Kafka 3.x+）；若对接旧版 Broker（如现网 0.10.x/1.x，无 INIT_PRODUCER_ID 协议），
+      # 经 MSGX_KAFKA_ACKS=1 与 MSGX_KAFKA_IDEMPOTENCE=false 降级兼容。
+      acks: ${MSGX_KAFKA_ACKS:all}
+      enable-idempotence: ${MSGX_KAFKA_IDEMPOTENCE:true}
+      max-in-flight-requests-per-connection: ${MSGX_KAFKA_MAX_IN_FLIGHT:5}
 eureka:
   client:
     registration: