Treasure Map Tweaks

English:
- Added a white distance label with a dark background on treasure maps.
- Added off-map player direction arrows.
- Added per-player treasure location uniqueness.

中文：
- 为藏宝图添加带深色背景的白色距离标签。
- 添加地图外玩家朝向箭头。
- 添加按玩家区分的藏宝地点去重。