docs: Add comprehensive PKCS#11 spy integration guide

- Detailed comparison of pkcs11-spy vs observe-core approaches
- Before/after log format examples (plaintext vs structured JSON)
- Configuration examples for both SoftHSM2 and Kryoptic
- Use cases: debugging, performance analysis, security auditing
- Best practices and troubleshooting guide
- Integration examples for CI/CD workflows

Author: testingapisname