feat: enable SSE streaming support in Anthropic handler

- Updated AnthropicHandler to check for streaming configuration before handling SSE transform.
- Modified handleStreaming to use the original request body instead of forcing stream to true.
- Adjusted the transformation logic in AnthropicToBifrost to respect the original stream setting.
- Added logging for SSE streaming configuration in the main application.

internal/transform/anthropic_bifrost.go

@@ -143,16 +143,11 @@ func AnthropicToBifrost(rawBody []byte) ([]byte, error) {
 		log.Printf("[TRANSFORM] Model auto-prefixed: %s -> %s", antReq.Model, model)
 	}
 
-	// Force stream=false — streaming SSE responses can't be transformed back to Anthropic format.
-	if antReq.Stream {
-		log.Printf("[TRANSFORM] Stream forced to false (SSE not supported for transform)")
-	}
-
 	bfReq := BifrostRequest{
 		Model:     model,
 		Messages:  bfMessages,
 		MaxTokens: antReq.MaxTokens,
-		Stream:    false,
+		Stream:    antReq.Stream,
 	}
 	return json.Marshal(bfReq)
 }