feat: scaffold Micronaut+Kotlin service per ACMA-8 v4 architecture

- 4 modules (ingress/processing/delivery/reference) + codec + infra + jobs
- Flyway V2.0.0: six aux tables (PROC_STATE/MSG_EVENT/REF_DATA/REQ_TRACK/PUMP_JOB/FLIGHT_STATE)
- Lua: snapshot_replace (atomic cover+gen-diff-delete), batch_delete (3:30 sweep)
- config: env-externalized secrets, phase A/B switch, ACMA-8 param-table defaults
- logback: logstash TCP JSON + traceId MDC
- pure-logic tests: identity (I3), schd aggregation max-by-EVENT_ID (FIX #7)
- build verified: gradle compile+test green on JDK 25 (Micronaut 5.1 requires JVM 25+)

Migrated from legacy repo subdirectory per repo-strategy decision (separate repo
per service, org convention). Refs: ACMA-9, ACMA-8 v4, ACMA-6

src/main/kotlin/com/gzzn/omms/msgexchange/nextgen/codec/XmlCodec.kt

@@ -0,0 +1,24 @@
+package com.gzzn.omms.msgexchange.nextgen.codec
+
+import com.gzzn.omms.msgexchange.nextgen.domain.DecodedMessage
+import com.gzzn.omms.msgexchange.nextgen.domain.ErrorClass
+
+/**
+ * ACMA-8 流程 2：解码失败分类（矩阵/状态机：MALFORMED 不重试；CODEC_ERROR 可一键重放）。
+ */
+data class DecodeFailure(val errorClass: ErrorClass, val detail: String)
+
+sealed interface DecodeResult {
+    data class Ok(val message: DecodedMessage) : DecodeResult
+    data class Err(val failure: DecodeFailure) : DecodeResult
+}
+
+/**
+ * XML codec：XXE 防护（禁 DTD/外部实体）；阶段 1 先 vendor 复用 legacy entity/msg POJO +
+ * jackson-dataformat-xml + JaxbAnnotationIntrospector（现役已验证组合，ACMA-6 选型）。
+ * TODO(阶段1后续): vendor POJO 引入与 BDPB workaround 配置化（golden 固化）。
+ */
+interface XmlCodec {
+    fun decode(rawXml: String): DecodeResult
+    fun encodeRqrd(kind: String, rangeJson: String): String
+}