Add OpenAI compatibility support and improve resource cleanup

- Introduced OpenAI compatibility configurations for external providers, enabling model alias routing via the OpenAI API format.
- Enhanced provider logic in `GetProviderName` to handle OpenAI aliases and added new helper functions for compatibility checks.
- Updated API handlers and client initialization to support OpenAI compatibility models.
- Improved resource cleanup across clients by closing response bodies and streams using deferred functions.

internal/api/handlers/openai/openai_handlers.go

@@ -278,7 +278,7 @@ outLoop:
 			// Handle client disconnection.
 			case <-c.Request.Context().Done():
 				if c.Request.Context().Err().Error() == "context canceled" {
-					log.Debugf("Client disconnected: %v", c.Request.Context().Err())
+					log.Debugf("qwen client disconnected: %v", c.Request.Context().Err())
 					cliCancel() // Cancel the backend request.
 					return
 				}