fix: use database-side filtering and enterprise-scoped detail queries

- Push provider_id filtering into database via current_set().filter()
  instead of iterating all configs in Python.
- Scope SAMLProviderData detail lookups by entity_id to prevent
  cross-enterprise data access by guessing IDs.

ENT-11567

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