fix: upgrade Gradle and plugins for Java 25 compatibility

[postyizhan]

Background

The original project setup uses outdated Gradle and plugin versions that are incompatible with Java 25. Attempting to build the project with the default configuration results in build failures due to unsupported class file versions and plugin resolution issues.

Issues with original setup

• com.gtnewhorizons.gtnhsettingsconvention plugin version 1.0.27 is incompatible with Java 25.
• Gradle version 8.9 lacks support for Java 25 class files.
• The dts.typescript-generator plugin is referenced without a version and fails to resolve.
• Code contains API usages that no longer match the latest library definitions, causing compilation errors.
• Git submodules required for build were not initialized by default, causing missing source errors.

Changes made

• Upgraded gtnhsettingsconvention plugin to 2.0.29 which supports Java 25.
• Updated Gradle wrapper to 9.3.1, enabling proper Java 25 support.
• Fixed plugin resolution for dts.typescript-generator by enabling the resolution strategy and specifying version explicitly.
• Replaced deprecated archivesBaseName with base.archivesName to comply with Gradle's newer conventions.
• Initialized Git submodules (gradle-plugins and src/api) to include all required code during build.
• Corrected outdated API calls in CustomNpcs.java by removing nonexistent methods and adjusting parameters.

Verification

• Successfully built locally with Java 25.
• Verified that all expected tasks compile and package as intended.

This PR ensures the project can be built and developed using a modern Java 25 environment, resolving critical compatibility blocks present in the original repo configuration.If you prefer to continue building with Java 8, please let me know, and I can help adjust the setup accordingly.