Add 18 test functions for admin custom services CRUD handlers, 6 tests for admin booking creation with custom services, and 5 tests for booking custom service integrations (confirm overrides, get, validation, progress). Also fix FK constraint issues in test request creation.
Ultraworked with Sisyphus (https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
