feat: add rpc_find_match for basic 2-player matchmaking

- Implement rpc_find_match Nakama RPC function
- Search for existing authoritative TicTacToe matches via MatchList
- Return first match with available slot (size < 2)
- Create new match using MatchCreate when none available
- Add request/response structs for future extensibility
- Log match search, selection, and creation flow
- Gracefully handle optional JSON payload and invalid input

plugins/main.go

@@ -34,6 +34,10 @@ func InitModule(
 		logger.Error("Failed to register RPC: %v", err)
 		return err
 	}
+	if err := initializer.RegisterRpc("rpc_find_match", rpcFindMatch); err != nil {
+		logger.Error("RegisterRpc rpc_find_match failed: %v", err)
+		return err
+	}
 
 	logger.Info("Go module loaded successfully!")
 	return nil