fix(recovery): the database dumps count in the keys the backups still need

The recovery kit, "Keys the backups still need" and safeToDropRetiredKeys
read only the stored copies and the off-host account objects. After a
rotation the page called the old key safe to drop while every dump taken
before it, the pre-migration dumps that are the way back from an update
among them, could only be restored with that key: db-restore refuses a dump
whose active key is missing.

A dump now counts for the key its rows were written under, the manifest's
active key: a dump on this server while it is kept (read from the manifests),
an off-host one until the bucket's rule for database/ expires it, or
indefinitely when that rule cannot be read. The nightly run records the key
on its ledger row (migration 0489, database_backup_runs.active_key_id). The
encryption view and the kit list the dumps per key, in every locale, and the
rotation and backup runbooks say so.

scripts/seed-demo.ts

@@ -3975,6 +3975,7 @@ export async function seed() {
           stored: [],
           unrecorded: { copies: 0, oldestAt: null },
           offhost: [],
+          dumps: [],
           offhostExpirationDays: null,
           retiredKeysStillNeeded: [],
         },