Port to 26.1: Java 25, Mojmap

[fnltochka]

Changes:

• Bumped versions
• Fixed mapping changes
• CI: Switched to Zulu 25 (Temurin 24+ drops jmods, breaking ProGuard)

Status:

• CI (gradle_build, run_tests)
• Fabric
• Forge
• NeoForge

TODO:

• Fix Forge, broken by Unimined: issues

[Dehowy]

I have been looking forward to this version for a long time, 26.1 with fabric. Thank you for your contribution. Please allow me to fork your code and build it before your pull request is approved.

[Big-Iron-Cheems]

Out of curiosity, is there a particular issue (or set of issues) in Unimined that is blocking the progress for Forge/NeoForge updating?
Thanks for the swift work on the Fabric side in the meantime.

[AndreNijman]

I rebased this onto the current 1.21.11 tip and finished the loaders in #5061 (your commits are preserved). The base's recent update unimined & gradle commit is what unblocked Forge — all three loaders (Fabric/NeoForge/Forge) now build on JDK 25, and :test passes. Happy to fold it back into this PR instead if you'd prefer — whatever's easiest for landing it.