Release v4.1.0

[vycdev]

Summary

Release Kromacut v4.1.0 from develop into main.

• Twelve languages across the app, illustrated guides, public pages, and update notes, with persistent language selection and locally bundled fonts.
• Adaptive Stack Matrix calibration with one-first-layer foundations, grouped recipes, and preserved saved-board compatibility.
• More conservative isolated-speck cleanup, plus effective line width in 3D Print Settings.
• Restored desktop Hiding Distance STL/3MF downloads.
• Privacy and Terms pages, a custom 404 page, and the mobile landing-page launch action.
• Linux AppImage update information and matching .zsync assets for compatible external delta-update tools.
• Synchronized release metadata and publication checks that hold website/update-feed deployment until desktop downloads are published.

References #2 and #78. AnyLinux packaging is deferred and is not included.

Compatibility

Existing profiles and current calibration records remain compatible. New Stack Matrix layout/foundation rules apply only to newly generated matrices. Back up important profiles and check regenerated prints in the slicer. Older AppImages need a one-time manual download before external delta-update tools can use the new metadata.

Validation

• 690 Node regression tests passed on the app-change commit; release preparation adds 10 passing metadata/deployment regression tests.
• Production build and all 4 production i18n browser tests passed.
• 28 focused release/AppImage/i18n/docs tests, 6 Rust tests, lint, and workflow validation passed.
• Earlier app verification: 17 i18n browser tests and 4 line-width/detail-conservation browser tests passed.
• Linux fixture packaging and byte-identical zsync reconstruction passed; full native artifacts will be built by release CI.
• Production npm audit is clear. Development-tooling alerts remain deferred by request; release preparation did not change dependencies.

Release sequence

1. Merge this PR after the required branch-direction check.
2. Tag the merge commit as v4.1.0 and push the tag.
3. Verify every native build and the published release assets.
4. Verify the follow-up Pages deployment and live update feed.

Private audit notes and local calibration/temporary files are excluded. Packaged-app runtime testing on every OS is not claimed.