1.4.8

release: 1.4.8 — friendly update errors + draft-release CI

User just clicked Check for Updates during the 3-min window between
the windows job uploading first and the macOS notarize finishing,
and saw:

  'Cannot find latest-mac.yml in the latest release artifacts (
   https://github.com/osmove/backlog/releases/download/v1.4.7/
   latest-mac.yml): HttpError: 404 …'

Two fixes shipped together:

1. humanizeUpdateError() in main.ts
   Classifies known electron-updater error patterns and replaces them
   with one-line French guidance:
   - missing platform manifest → 'La nouvelle version est en cours
     de finalisation. Réessaye dans 2-3 minutes.'
   - network → 'Pas de connexion internet'
   - rate-limit / 403 → 'GitHub limite temporairement les requêtes'
   - disk full → 'Espace disque insuffisant'
   - signing mismatch → 'Télécharge manuellement depuis backlog.so'
   - generic fallback → 'Mise à jour indisponible pour l'instant'

   The raw message stays in a tooltip (status.detail) for power users
   and bug reports.

2. CI: draft releases until all platforms uploaded
   The actual race fix. electron-builder.yml releaseType is now draft;
   each platform job uploads into a hidden release. A new
   finalize-release job runs after linux+macos+windows all succeed,
   sanity-checks every expected artifact is on the release (DMGs,
   exes, AppImages, latest-*.yml manifests), then flips
   draft -> published. If anything is missing, the draft is left up
   for manual inspection instead of shipping a half-baked release.
   Auto-update clients now see new versions appear atomically.