fix: explain empty location loads

[krowvin]

Summary

• return a friendly message when a load location source query returns no locations
• point users toward refining --like / --location-kind-like and checking filters in CDA Swagger or the regex guide
• avoid initializing the target session or reporting a misleading success path when there is nothing to copy

Resolves #186

Validation

• poetry run pytest tests/commands/test_load_location_ids.py -q
• poetry run pytest -q
• poetry check