chore: Add Gradle wrapper checksum verification (GRADLE-104)

Adds distributionSha256Sum to gradle-wrapper.properties so the Gradle
wrapper verifies the integrity of the downloaded distribution against a
known-good SHA256 before using it.

Author: runningcode

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionSha256Sum=7197a12f450794931532469d4ff21a59ea2c1cd59a3ec3f89c035c3c420a6999
 distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.2-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true