Hardcoded SELECT_QUERY_TIMEOUT_SECS=30

[Arturus]

I can't execute heavy queries with MCP because it always fails with error 'Query timed out after 30 seconds'.
Query timeout is hardcoded in mcp_server.py to 30 seconds. It should be configurable or at least have reasonable default value equal to default CLICKHOUSE_SEND_RECEIVE_TIMEOUT (600 seconds)