* fix(cron): handle legacy atMs field in schedule when computing next run
The cron scheduler only checked for `schedule.at` (string) but legacy jobs
may have `schedule.atMs` (number) from before the schema migration.
This caused nextRunAtMs to stay null because:
1. Store migration runs on load but may not persist immediately
2. Race conditions or file mtime issues can skip migration
3. computeJobNextRunAtMs/computeNextRunAtMs only checked `at`, not `atMs`
Fix: Make both functions defensive by checking `atMs` first (number),
then `atMs` (string, for edge cases), then falling back to `at` (string).
This ensures jobs fire correctly even if:
- Migration hasn't run yet
- Old data was written by a previous version
- The store was manually edited
Fixes#9930
* fix: validate numeric atMs to prevent NaN/Infinity propagation
Addresses review feedback - numeric atMs values are now validated with
Number.isFinite() && atMs > 0 before use. This prevents corrupted or
manually edited stores from causing hot timer loops via setTimeout(..., NaN).
b0befb5f5d