No ubi while afk

Goal

Don't pay recurring basic-income / salary to AFK players.

Grounded

Recurring gov payouts run in SalaryServiceImpl.planPayroll() (treasury/.../services/impl/SalaryServiceImpl.java:59): it iterates server.getOnlinePlayers(), resolves each player's highest LuckPerms-group salary, then payout(...) transfers from the gov account. There is no AFK check, so AFK-idling players still collect.

Fix

In planPayroll(), skip AFK players before resolving their salary. AFK signal options:

• Essentials (the server runs Essentials): User.isAfk() via the Essentials API (IUser.isAfk() exists).
• LuckPerms context (per the issue title): if an afk context is registered, gate on it. Make it configurable (some setups may want to keep paying AFK players).

Acceptance

• An AFK player is excluded from a payroll cycle; non-AFK players unaffected.
• A toggle to disable the AFK gate.