Enable Maven wrapper SHA-256 integrity verification

Populate wrapperSha256Sum and distributionSha256Sum in
maven-wrapper.properties so mvnw/mvnw.cmd validate the downloaded
wrapper jar and Maven distribution, protecting CI and developer
machines from compromised downloads.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ramsessanchez

.mvn/wrapper/maven-wrapper.properties

@@ -1,2 +1,4 @@
 distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.9/apache-maven-3.9.9-bin.zip
+distributionSha256Sum=4ec3f26fb1a692473aea0235c300bd20f0f9fe741947c82c1234cefd76ac3a3c
 wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.3.2/maven-wrapper-3.3.2.jar
+wrapperSha256Sum=3d8f20ce6103913be8b52aef6d994e0c54705fb527324ceb9b835b338739c7a8