refactor: moved registries into a separate module and code cleanup

fix: refactored dial provider to follow the same pattern

tests/test_o3_temperature_fix_simple.py

@@ -7,7 +7,7 @@ for O3 models while maintaining them for regular models.
 
 from unittest.mock import Mock, patch
 
-from providers.openai_provider import OpenAIModelProvider
+from providers.openai import OpenAIModelProvider
 
 
 class TestO3TemperatureParameterFixSimple:
@@ -175,7 +175,7 @@ class TestO3TemperatureParameterFixSimple:
     @patch("utils.model_restrictions.get_restriction_service")
     def test_all_o3_models_have_correct_temperature_capability(self, mock_restriction_service):
         """Test that all O3/O4 models have supports_temperature=False in their capabilities."""
-        from providers.openai_provider import OpenAIModelProvider
+        from providers.openai import OpenAIModelProvider
 
         # Mock restriction service to allow all models
         mock_service = Mock()
@@ -211,7 +211,7 @@ class TestO3TemperatureParameterFixSimple:
     @patch("utils.model_restrictions.get_restriction_service")
     def test_openai_provider_temperature_constraints(self, mock_restriction_service):
         """Test that OpenAI provider has correct temperature constraints for O3 models."""
-        from providers.openai_provider import OpenAIModelProvider
+        from providers.openai import OpenAIModelProvider
 
         # Mock restriction service to allow all models
         mock_service = Mock()