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.

main.go

@@ -160,6 +160,7 @@ func main() {
 	if db != nil {
 		log.Printf("   DB logging      : enabled")
 	}
+	log.Printf("   SSE streaming   : %v", cfg.Streaming)
 
 	if err := app.Listen(addr); err != nil {
 		log.Fatalf("server error: %v", err)