refactor: moved registries into a separate module and code cleanup

fix: refactored dial provider to follow the same pattern

tests/test_alias_target_restrictions.py

@@ -9,7 +9,7 @@ import os
 from unittest.mock import patch
 
 from providers.gemini import GeminiModelProvider
-from providers.openai_provider import OpenAIModelProvider
+from providers.openai import OpenAIModelProvider
 from providers.shared import ProviderType
 from utils.model_restrictions import ModelRestrictionService