chore(deps): Update Minestom to 2025.10.05-1.21.8 to use new APIs

[ajh123]

This pull request updates the Minestom server integration to use the new authentication API and improves configuration handling. The most significant changes are the migration to the latest Minestom version for Java 21, refactoring of proxy authentication logic, and the addition of new utility methods.

Minestom Authentication and Proxy Refactor:

• Replaced the old BungeeCordProxy and VelocityProxy setup with the new Auth API from Minestom, centralising authentication configuration in the new getConfiguredAuth() method. The server is now initialized with an Auth instance based on configuration, and logs the configured auth type. (ShulkerServerAgentMinestom.kt) [1] [2]

Utility and API Improvements:

• Added a public getConfiguredAuth() method to allow consumers to query the current authentication type. (ShulkerServerAgentMinestom.kt)
• Added a getInstance() static method to ShulkerServerAgentMinestom to allow consumers to actually query the authentication type. (ShulkerServerAgentMinestom.kt)

Dependency Updates:

• Upgraded the Minestom library dependency to net.minestom:minestom:2025.10.05-1.21.8 to support the new authentication API. (settings.gradle.kts) IMPORTANT: This version is the latest Minestom version to support Java 21, newer versions like net.minestom:minestom:2025.10.18-1.21.10 require Java 25
• The PR of fix(deps): update dependency net.minestom:minestom-snapshots to v7320437640 #636 should be closed as Minestom has changed how their dependencies are managed since that PR.