Add M5Stick S3 board support and local build fixes

[GradusXaker]

Summary

• add full board support for M5Stick S3, including board metadata, pins and interface integration
• fix local firmware build setup for m5stack-cplus2 and align helper scripts used in the Gradus fork
• add release notes for the unified firmware release and the new Stick S3 target

Why

These changes sync the local build workflow with the new targets and make M5Stick S3 available as a first-class board configuration.

Scope

• board definitions and configuration files
• local build helper updates
• release notes only; no unrelated changes included

[GradusXaker]

Hi! This PR adds M5Stick S3 board support and includes the small local build fixes needed to keep the Gradus fork aligned with the new targets.

What is included:

• M5Stick S3 board definitions, pins and interface integration
• local build fixes for m5stack-cplus2
• release notes for the unified firmware release and the new Stick S3 target

I tested this in the fork workflow and limited the scope to board/build-related changes only.
If you prefer, I can split the release notes into a separate PR.