Add admin/stats users to PgBouncer config for SHOW commands

Without admin_users/stats_users, connecting to the pgbouncer virtual
database fails with "database pgbouncer does not exist".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/pgsql/pgbouncer-dev.ini

@@ -17,3 +17,5 @@ server_idle_timeout = 600
 log_connections = 0
 log_disconnections = 0
 ignore_startup_parameters = extra_float_digits
+admin_users = app
+stats_users = app