app: Revert electron-builder version bump

[Oleksandr Dubenko (sniok)]

this pr reverts electron-builder version bump and build configuration

[Copilot]

Pull request overview

This pull request reverts the electron-builder package from version 26.6.0 back to version 24.13.3, along with reverting associated build configuration changes. The primary motivation appears to be addressing compatibility or build issues introduced by the newer version.

Changes:

• Downgraded electron-builder from ^26.6.0 to ^24.13.3
• Reverted Windows signing configuration from nested signtoolOptions.sign structure to direct sign property
• Updated package-lock.json with all transitive dependencies matching the older electron-builder version

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
app/package.json	Reverted electron-builder version and Windows signing configuration format
app/package-lock.json	Updated dependency tree to match electron-builder v24.13.3 and its transitive dependencies

The changes are internally consistent - the signing configuration change from signtoolOptions: { sign: "windows/sign.js" } to sign: "windows/sign.js" aligns with the API differences between electron-builder v26 and v24. The referenced windows/sign.js file exists and is properly implemented.

The package-lock.json shows a clean reversion with:

• Removal of newer dependencies introduced by v26 (e.g., @electron/rebuild, @electron/fuses, node-gyp v11)
• Restoration of older dependency versions compatible with v24
• Addition of dependencies that v24 requires (e.g., bluebird-lst, form-data in electron-publish)

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[René Dudfield (illume)]

🎉 thanks!

[René Dudfield (illume)]

Frontend failures are fixed in another PR.