Pause/resume game as admin

[jasonappah]

Summary
Add admin-only ability to pause and resume a game. Pausing halts clocks, engine processing, and robot/simulator I/O; all clients are notified.

Details

• Server endpoints and/or socket events to pause/resume a given game id
• Update game-manager to support a paused state and idempotent transitions
• Ensure enforcement within simulator and robot control layers while paused
• Broadcast state changes to clients and reflect in the admin UI

Acceptance Criteria

• Calling pause on an active game transitions it to paused; resume returns to prior state
• While paused, no moves are executed, no time elapses, and hardware I/O is suspended
• Unit tests for state transitions; basic integration via simulator path

Notes

• Likely touches: src/server/game-manager.ts, simulator.ts, robot-manager.ts, socket messaging.