Added default orphan cleanup configuration

Implemented default configuration support for orphan cleanup settings during module installation.

Changes made

• Added default configuration file:
  • config/install/block_content_explorer.settings.yml
• Added default values for:
  • auto_cleanup_enabled
  • cleanup_interval_days
  • max_blocks_per_cron
• Verified configuration schema definitions for cleanup settings in:
  • config/schema/block_content_explorer.schema.yml