Migrate SQL Rule Type to use postgresql (after sql refactor)

SQL Rule Type will initially use duckdb to execute queries. After the refactor, we can switch to using postgresql which will replace pandas/dask.

This will involve converting any duckdb flavor sql to postgresql flavor.

Start by locating the SQL Rule Type and reviewing the referenced SQL refactor. Identify where DuckDB execution and pandas/dask usage are handled, then determine the PostgreSQL flavor conversions required. Done means the refactored SQL Rule Type executes through PostgreSQL and no longer relies on DuckDB for this path.

Written by the indexing model from the issue text.