Update MMDLib 1.12 to the Base Metals FG7 build setup

[SkyBlade1978]

This updates MMDLib's 1.12.2 build to the ForgeGradle 7 setup used by Base Metals, with matching toolchains, pinned dependencies, reproducible jars and GitHub Actions checks and release workflows.

The Java implementation and Maven coordinate now use zone.moddev.mc.mmdlib. A Forge compatibility adapter keeps existing com.mcmoddev.lib consumers working with the same library state. Mod IDs, registries, configuration and gameplay behavior are preserved. The README, changelog and code comments are updated, and local notes and generated output are excluded.

Checked locally with 39 tests, the 500-class legacy API audit, clean offline builds, reproducibility, Javadocs, Eclipse setup and packaged client/server profiles with Base Metals and optional integrations. IC2 was tested separately because its existing bronze-recipe conflict with the full machine stack also occurs with published MMDLib. The build guide records the commands and results; hosted checks are separate.

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