fix(lib/server): use the instance source in player.getState

[DoluTattoo]

Problem

PlayerInterface.getState reads the global source instead of the instance property:

getState() {
  return Player(source).state;
}

Looks like an oversight: the constructor already assigns this.source, and every other method uses it. Whenever the instance is used outside of a handler for that same player, getState returns another player's state bag, and writes land on the wrong entity.

Fix

getState() {
  return Player(this.source).state;
}

lib/server/player.lua already does this, and lib/server/vehicle.ts resolves its state bag from this.entity.

Impact

No API change. Calls that were correct by accident keep working; the others now target the intended player.