refactor: rename package to dev.nucleusframework.composenativetray

[kdroidFilter]

Summary

• Rename the base package from `com.kdroid.composetray` to `dev.nucleusframework.composenativetray` across all source sets (main, test, demo).
• Update native JNI sources so exported symbols and `FindClass` lookups match the new package:
  • `src/native/windows/jni_bridge.c`, `src/native/linux/jni_bridge.c`
  • `src/native/macos/MacTrayBridge.m` (`JNI_PREFIX` macro + `MacNativeBridge$ThemeChangeCallback` lookup)
• Update GraalVM `reachability-metadata.json` reflected class names, proguard rules, `.run` configs, and README.
• Maven coordinates (`com.kdroid.composenativetray`) and the `composetray/` native resource folder are intentionally unchanged — they are not class paths.

Test plan

• `compileKotlinJvm`, `compileTestKotlinJvm`, `:demo:compileKotlinJvm`
• `jvmTest`
• Rebuilt Windows DLLs (x64 + ARM64) and verified exported symbols are now `Java_dev_nucleusframework_composenativetray_...`
• CI native builds for Linux/macOS from updated sources