feat(setup): harden Python bootstrap across dev and packaged installs

[KevinEightSeven]

Summary

• add GPU-aware PyTorch index selection during setup and remove hardcoded index coupling in Python requirements
• fix dev setup bootstrapping to create and use api/.venv consistently (including Windows dev mode)
• harden Python/venv discovery and packaged venv creation (including AppImage-safe --clear --copies behavior)
• compile app C++ extensions during setup and expose additional setup progress stages in the UI
• include changelog and project context updates for this release work

[lightningpixel]

Thanks for your contribution !

However, before merging the PR, you’ll need to rebase onto the dev branch (it’s the branch that receives all changes, while main is the production branch corresponding to the latest release). You’ll likely have some conflicts to resolve with the new version.

After that, please remove the CHANGELOG.md, CLAUDE.md, and package-lock.json files.