[build] Fix Kafka shaded JAR license layout

Preserve the Kafka NOTICE under META-INF and exclude duplicate root legal files.

Co-Authored-By: Codex <noreply@openai.com>
AI-Model: gpt-6
AI-Contributed/Feature: 34/34
AI-Contributed/UT: 0/0

Author: gyang94

fluss-kafka/pom.xml

@@ -137,6 +137,17 @@
                                     <include>org.apache.kafka:kafka-clients</include>
                                 </includes>
                             </artifactSet>
+                            <filters>
+                                <filter>
+                                    <artifact>org.apache.kafka:kafka-clients</artifact>
+                                    <excludes>
+                                        <!-- Apache 2.0 is in META-INF/LICENSE; retain Kafka's
+                                             NOTICE in META-INF/licenses/NOTICE.kafka-clients. -->
+                                        <exclude>LICENSE</exclude>
+                                        <exclude>NOTICE</exclude>
+                                    </excludes>
+                                </filter>
+                            </filters>
                             <!-- Retain Kafka classes loaded reflectively. -->
                             <minimizeJar>false</minimizeJar>
                             <shadedArtifactAttached>false</shadedArtifactAttached>

fluss-kafka/src/main/resources/META-INF/licenses/NOTICE.kafka-clients

@@ -0,0 +1,23 @@
+Apache Kafka
+Copyright 2026 The Apache Software Foundation.
+
+This product includes software developed at
+The Apache Software Foundation (https://www.apache.org/).
+
+This distribution has a binary dependency on jersey, which is available under the CDDL
+License. The source code of jersey can be found at https://github.com/jersey/jersey/.
+
+This distribution has a binary test dependency on jqwik, which is available under
+the Eclipse Public License 2.0. The source code can be found at
+https://github.com/jlink/jqwik.
+
+The streams-scala (streams/streams-scala) module was donated by Lightbend and the original code was copyrighted by them:
+Copyright (C) 2018 Lightbend Inc. <https://www.lightbend.com>
+Copyright (C) 2017-2018 Alexis Seigneurin.
+
+This project contains the following code copied from Apache Hadoop:
+clients/src/main/java/org/apache/kafka/common/utils/PureJavaCrc32C.java
+Some portions of this file Copyright (c) 2004-2006 Intel Corporation and licensed under the BSD license.
+
+This project contains the following code copied from Apache Hive:
+streams/src/main/java/org/apache/kafka/streams/state/internals/Murmur3.java