Improve Gradle build performance

Enable Gradle build caching and parallel execution, increase JVM memory allocation for better build performance across all example projects.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: nakamura-to

gradle.properties

@@ -1,7 +1,11 @@
 kotlin.code.style=official
-org.gradle.jvmargs=-Xmx2560m
+
 ksp.incremental=true
 ksp.useKSP2=true
 
+org.gradle.caching=true
+org.gradle.jvmargs=-Xmx4096m -XX:MaxMetaspaceSize=1024m
+org.gradle.parallel=true
+
 group=org.komapper
 version=0.0.1