Add Authorization layer

[ondrej-lukas]

Implement the access control and authorization layer

[verovaleros]

Concrete authorization gap to track under this issue: GameCoordinator._dispatch_action (netsecgame/game/coordinator.py:285-298) forwards all game action types (ScanNetwork, ExploitService, BlockIP, etc.) into _process_game_action without checking the sender's registered role. As a result, role identity does not constrain action class (e.g., Defender can execute attacker actions).

Related security report with repro/context: #482.