Retrieves the effective policies that actually apply to a tenant.
This considers the inheritance chain and returns the final policy
that would be enforced for cryptographic operations.

Effective policy resolution:

1. If tenant has custom policy → use tenant policy
2. If no tenant policy → use deployment policy
3. If no deployment policy → use system defaults

This endpoint is essential for:
• Understanding what policies are actually enforced
• Debugging policy inheritance issues
• Validating policy configuration