Prune persistentIds older than 24h so config.json stops growing

[cassiostp]

Every delivered push appends a persistentId to config.json and the list is never trimmed, so the file grows without bound and electron-config rewrites all of it synchronously on the main process for each push. Across 46.6k native devices (log.push_receiver_config_stats, Sep 8–15) the darwin p50 is 53.7k ids / 2.2 MB and the p99 is 981k ids / 40 MB. At the median ~360 pushes per active day, a median device serialises ~0.8 GB/day of JSON on the UI thread.

Fix

Each id is 0:{microsecondTimestamp}%{hash}, so its age is known. pruneStale drops ids older than 24 h from the list seeded into listen() at start and from every append.

24 h is safe because the list only prevents the server from redelivering pushes on the next login, and the backend sends desktop pushes with TTL: 5 minutes (new-email, calendar-event) or TTL: 0 (history, userdata-history) (mail-backend/lib/notifications/notify.go). Nothing older can be replayed; the margin covers clock skew. Ids that do not parse are dropped so a format change cannot reintroduce unbounded growth.

webContents.send calls are guarded with isDestroyed().

Rollout

Publish as 2.1.10 and bump native/package.json in desktop. The first login after upgrade sends the pruned list. Rollback is a version revert; the old code reads the same array. Expected signal in log.push_receiver_config_stats: persistent_ids_count p50 from ~50k to a few hundred, config_bytes p50 from 2.2 MB to under 50 KB.

CLI-2311

[linear-code]

CLI-2311

[zindlerb]

I would keep existing behaviour here where if we don't pass in credential we raise an error.