feat(commands): unify settings and admin commands

design/user-stories/us-008-unlock-visitor-access.md

@@ -12,12 +12,11 @@ As a **player with Base III**, I want to open my base to visitors so that other
 ## Acceptance criteria
 
 - [x] Base IV requires Base III and an established base.
-- [x] `/base upgrade` offers the Base IV purchase for a configurable price that defaults to 128 diamonds.
+- [x] `/basesettings upgrade` offers the Base IV purchase for a configurable price that defaults to 128 diamonds, replacing `/base upgrade` and `/home upgrade`.
 - [x] A successful purchase removes the complete price atomically from the player's direct inventory.
 - [x] Insufficient funds, an invalid state, or a failed persistence operation does not consume any diamonds or grant Base IV.
-- [x] `/basevisitors` lets a Base IV owner toggle visitor access on and off.
-- [x] `/basevisitors on` enables access idempotently and `/basevisitors off` disables it idempotently, with `on` and `off` offered through autocomplete.
-- [x] `/homevisitors` aliases `/basevisitors` with identical behavior and autocomplete.
+- [x] `/basesettings visitors allowed` permits visitor access idempotently for a Base IV owner, and `/basesettings visitors blocked` blocks it idempotently.
+- [x] Invalid visitor arguments show command usage, and `allowed` and `blocked` are offered through autocomplete.
 - [x] The visitor-access preference persists across reconnects and restarts.
 - [x] `/gotobase <owner>` autocompletes bases that the requesting player is currently eligible to visit.
 - [x] `/visit <owner>` aliases `/gotobase <owner>` with identical autocomplete, including eligible bases whose owners are offline.