Every shard is sealed with the web database’s key

One key for all shards: the web database’s (today’s pairing), so there is one key to back up and re-key. The key’s home is D-15’s.

Provenance: technical default selected by the coordinator, described in the original conversation at line 5525 (2026-10-01), not an option accepted by the user in answer 5469. The later storage/durability approval at 5760 does not retrospectively turn this selection into a direct user answer.