Update user's enabled states

Update the list of states (geographic regions) that a user is enabled to work in.

Authentication Required: Yes Permissions: User must be updating their own states or have admin permissions

Request Body:

{
    "states": ["state1", "state2", "state3"]
}

Process:

1. Validates the states data
2. Immediately updates cache
3. Writes to database immediately if worksite filters changed, otherwise schedules a flush task (USER_STATES_FLUSH_DELAY)
4. Returns immediate confirmation

Note: Updates are cached immediately. Filter changes are persisted to the database immediately; other changes are persisted by a delayed flush task.