feat(lobby): add mesh check retries and improve QuickMatch setup

[tintinhamans]

Add one retry for failed mesh checks in custom lobbies and use the same mesh check before starting QuickMatch.

Each check keeps the existing five-second timeout. If the first check fails, the server restarts signalling for the missing peer connections, waits three seconds for them to reconnect, and runs one final check.

QuickMatch runs the mesh check during its existing countdown. The game starts when the mesh succeeds; otherwise, the temporary lobby is removed and the players are requeued.

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• retry failed mesh checks once
• restart signalling only for missing connections
• correlate responses with a check ID and attempt number
• ignore late responses from previous attempts
• treat clients that do not respond as disconnected
• make matchmaking cancellation, cleanup, and requeue handling safer

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Clients in the lobby	Behavior
All updated	The server can retry once and safely match responses to each attempt
Any legacy client responds	The server accepts its response for the first attempt and skips the retry
A client does not respond	The server treats it as disconnected and fails after the available attempts

Legacy clients can still complete mesh checks, but they do not understand the new setup-progress or requeue messages. They may still show the existing 10-second warning while the server is working and recover through the normal teardown and next-lobby flow.

Together with GameClient PR #570, this prevents QuickMatch from starting with an incomplete peer mesh while allowing transient signalling failures to recover without forcing players to restart matchmaking.