A test proves /admin settings and moderators survive a relay restart on the same FORGE_APP_DATA #136

Part of #12, which is mostly on main (5d4fef3, pull #45). Owner's test list: "changes persist across restart". src/admin.test.ts covers the store; nothing covers the relay.

Done:

• [ ] New Software/so101/src/admin-restart.test.ts: start a relay on a temp data dir; the owner saves a setting and names a moderator through POST /admin; stop it, start a new relay on the same dir; GET /admin as the owner shows the setting, the moderator and the change log entry with who made it; the moderator still sees /admin and still cannot save.
• [ ] Test-only: no change outside the new file. bun --cwd Software/so101 test passes.