chore: Update sql_saga to 9e39fcc (security + bug fixes after agent review)

Notable changes:
- Fix C bugs, add audit comments, deduplicate FK check code
- Fix Rust bugs, add audit comments, deduplicate qi()
- Add SET search_path to all SECURITY DEFINER functions
- Add tests for set_era_ephemeral_columns and first() aggregate

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jhf

postgres/Dockerfile

@@ -16,7 +16,7 @@ ARG wal2json_release=wal2json_2_6
 ARG pg_hashids_release=cd0e1b31d52b394a0df64079406a14a4f7387cd6
 ARG pgsql_http_release=v1.6.3
 ARG pg_trgm_release=1.6
-ARG sql_saga_release=82abdb6
+ARG sql_saga_release=9e39fcc
 ARG pg_stat_monitor_release=cd0feaf215e7236e3ffbe03458ce84c98b883a3f
 ARG pg_repack_release=23aac05f059e37fcbb9e006ab35fb376d79f434a
 ARG hypopg_release=1.4.1