feat: save external services incidents to db with status (#2202)

* feat: save external services incidents to db with status

* refactor: bulk upsert, tighter cron concurrency, prune index

* ci: apply automated fixes

* fix: address review feedback on external-incident upsert

* fix: validate prune TTL and handle incidents DB errors

* test: cover startedAt backfill + note api_config.endpoint scope

* chore: add adr + regenerate migration

* chore: remove type in col

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Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>