feat(recovery): judge the bucket's rule for database dumps in readiness

Only the backups page said when the bucket's lifecycle rules left
database/ out, so every dump, and every deleted account inside it, stayed
in the bucket forever without anyone being told. Readiness gains a
dump_retention signal that reads the same cached lifecycle probe: attention
when dumps go off-host and no rule covers database/, ok with the expiry
when one does, quiet when the bucket will not say, inactive without a
bucket or without off-host dumps. The hourly evaluation pushes it to the
admins like every other signal.

src/app/api/admin/recovery-readiness/route.ts

@@ -4,7 +4,8 @@
  * Every backup signal with its verdict, its time and where to fix it: the
  * database dump, the weekly copy, the off-host copies, the last restore drill
  * (no time window: a failed drill stays failed until a later one passes), the
- * off-host setup and the recovery kit. The same judgement the hourly
+ * off-host setup, whether the bucket ever removes the database dumps, and the
+ * recovery kit. The same judgement the hourly
  * evaluation pushes to the admins (`src/lib/recovery/readiness-model.ts`).
  * Cookie-only admin.
  */