fix: parse query_tags string into List[QueryTag] before passing to execute_statement

[yogesh-dbx]

Bug

execute_sql fails with 'str' object has no attribute 'as_dict' when query_tags is provided.

The SDK's StatementExecutionAPI.execute_statement() expects query_tags: Optional[List[QueryTag]], but executor.py passes the raw string directly.

Root Cause

executor.py line 88-89:

if query_tags:
    exec_params["query_tags"] = query_tags  # passes string, SDK expects List[QueryTag]