[Game Server] Add state machine validation to prevent invalid map status transitions

[Flegma]

Summary

UpdateMapStatus in MatchManager prevents duplicate transitions but does not validate that transitions are valid.

Findings

• MatchManager.cs — can transition from Warmup to Finished (skipping Live), Paused to Knife, etc. No allowed-transition map.

Impact

Match state corruption. Matches could end without being played or enter impossible states.

Suggested Fix

Define allowed transitions dictionary. Reject invalid transitions with warning log.