Close the economy's known gaps

The colonial economy (#121) is on main. Its Known gaps (docs/economy.md § 16) are left:

• Corpses and resource banks live in memory: a migration or failover loses them and the items in corpses. Make both durable in the store, fenced like objects.
• New characters on generated (test) worlds spawn by name hash instead of the synthetic free port; synthetic towns start at nearly the same prices.
• The load-test mix runs the economy bots against a ScyllaDB cluster (M7-style run, #89/#90) with a sim crash and a rolling restart: no duplicated items or coin, no lost corpses.

Done when the chaos run's report shows the coin and item totals conserved through failover.