PlayerStats & Group System v1.0.0

PlayerStats extended with full group management by Kaiser Fahim.

Create groups, invite members, compete on group leaderboards, and view live group stats
through the UI. Includes join snapshots (post-join stats only), auto-refreshing group panel,
leave/disband confirmations, auto owner transfer, and cross group info lookup. All original
PlayerStats features included with JSON/MySQL support.