refactor(multigres): run init-scripts as supabase_admin, remove postgres-role.sql

Both init-scripts and migrations now run as supabase_admin (the pgctld
cluster superuser), eliminating the need for a preamble SQL file to
pre-create the postgres role.

Author: mkindahl

Dockerfile-multigres

@@ -58,12 +58,6 @@ RUN rm -f \
     /home/postgres/wal_fetch.sh \
     /root/wal_change_ownership.sh
 
-# Preamble SQL run before init-scripts: creates the postgres role and sets DB ownership.
-# The wrapper script then passes --pg-initdb-sql-dir to run init-scripts (as postgres)
-# and migrations (as supabase_admin) in sorted order.
-# NOTE: --pg-initdb-sql-dir is not yet implemented in pgctld (MUL-484).
-COPY --chown=postgres:postgres docker/pgctld/postgres-role.sql /etc/pgctld-custom/postgres-role.sql
-
 # No HEALTHCHECK defined here: inherits the probe from the supabase base image.
 # Kubernetes ignores Docker HEALTHCHECK entirely — use readinessProbe in the Pod spec.
 # STOPSIGNAL inherited from supabase base image (SIGINT — smart shutdown).

docker/pgctld/pgctld

@@ -2,7 +2,6 @@
 # NOTE: --pg-initdb-sql-dir is not yet implemented in pgctld (MUL-484).
 exec /usr/local/bin/pgctld-bin \
   --postgres-config-template /etc/pgctld-custom/postgresql.conf.tmpl \
-  --pg-initdb-sql-files /etc/pgctld-custom/postgres-role.sql \
-  --pg-initdb-sql-dir postgres:/docker-entrypoint-initdb.d/init-scripts \
+  --pg-initdb-sql-dir supabase_admin:/docker-entrypoint-initdb.d/init-scripts \
   --pg-initdb-sql-dir supabase_admin:/docker-entrypoint-initdb.d/migrations \
   "$@"