This commit introduces a TOML catalog for managing dependencies and plugins, replacing inline version definitions.
It updates build scripts across the project to utilize the catalog, promoting consistency and simplifying dependency management.
Additionally, it configures repositories for plugin and dependency resolution in the settings file.

This commit updates several dependencies, including:
- Bumping BouncyCastle from 1.76 to 1.79
- Bumping kotlinx.datetime from 0.5.0 to 0.6.1
- Bumping Dokka from 1.8.10 to 1.9.20
- Bumping Kotlin from 1.9.22 to 1.9.25
- Bumping Krypto from 4.0.9 to 4.0.10
- Bumping MiniDNS from 1.0.3 to 1.1.1

It also updates the CI workflows to use:
- `actions/checkout@v4`
- `gradle/gradle-build-action@3`

I submit my source code and allow Tigase to release the code as a part of Tigase's own software package under any license, either an open source or closed source.

This commit introduces a convention plugin for multiplatform projects to centralize common configuration.

The plugin sets up the JVM toolchain, configures JVM and JS targets, and adds basic dependencies for common, JVM, and JS source sets.

Individual module build scripts now use the `kotlinMultiplatformConvention` plugin to apply this shared configuration.

I submit my source code and allow Tigase to release the code as a part of Tigase's own software package under any license, either an open source or closed source.