Remove the unreleased Electron desktop package

packages/apps-electron was never released, and electron 28, electron-builder
and their tooling (got, tar, app-builder-lib, builder-util-runtime) were most
of the dependency advisories left in this repo. Drop the package, its scripts,
the build:electron CI step, its i18n namespace and the deps only it used
(concurrently included).

The shipped web bundle changes by one string: "apps-electron" leaves the
i18n namespace list.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/pr-any.yml

@@ -6,7 +6,7 @@ jobs:
     continue-on-error: true
     strategy:
       matrix:
-        step: ['lint', 'test', 'build:code', 'build:i18n', 'build:electron']
+        step: ['lint', 'test', 'build:code', 'build:i18n']
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4