feat(phase-1): scaffold ChainLightning Sceptre plugin

Build infrastructure (Gradle wrapper, shadow, Java 25), manifest, item
JSON + interactions, and ChainLightningPlugin entry with stub handler
that logs sceptre clicks. Cooldown wiring deferred to Phase 3 (real
Hytale API is getCooldown(id).setCooldownMax — not cooldown(Duration)).

gradle.properties

@@ -0,0 +1,6 @@
+pluginGroup=com.mythlane
+pluginVersion=0.1.0
+pluginDescription=Hytale plugin - sceptre magique qui chaîne la foudre entre 5 cibles
+hytaleServerVersion=2026.03.26-89796e57b
+
+org.gradle.jvmargs=-Xmx1024m