build: fix gradlew and wrapper URL to work on any machine

gradlew was hardcoded to /home/amir/gradle/gradle-8.6/bin/gradle.
gradle-wrapper.properties used a local file:// URL.
Both now use the standard portable approach (HTTPS distribution URL)
so builds work in CI and on any dev machine without a local Gradle install.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gradlew

@@ -1,2 +1,39 @@
-#!/bin/bash
-exec /home/amir/gradle/gradle-8.6/bin/gradle "$@"
+#!/bin/sh
+##############################################################################
+# Gradle wrapper — standard portable launcher
+##############################################################################
+
+app_path=$0
+while [ -h "$app_path" ]; do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in
+      /*)   app_path=$link ;;
+      *)    app_path=${app_path%"${app_path##*/}"}$link ;;
+    esac
+done
+APP_HOME=$( cd "${app_path%"${app_path##*/}"}." && pwd -P ) || exit
+
+APP_BASE_NAME=${0##*/}
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+if [ -n "$JAVA_HOME" ]; then
+    JAVACMD=$JAVA_HOME/bin/java
+else
+    JAVACMD=java
+fi
+
+MAX_FD=maximum
+case "$( uname )" in
+  Darwin*) ;;
+  *)
+    MAX_FD=$( ulimit -H -n 2>/dev/null ) && ulimit -n "$MAX_FD" 2>/dev/null ;;
+esac
+
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS \
+    "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" \
+    -classpath "\"$CLASSPATH\"" \
+    org.gradle.wrapper.GradleWrapperMain '"$@"'
+
+exec "$JAVACMD" "$@"