New provider SiliconFlow and Its Latest DeekSeek Models

Update README.md

Update constant.ts

Update README_CN.md

app/api/auth.ts

@@ -101,6 +101,9 @@ export function auth(req: NextRequest, modelProvider: ModelProvider) {
       case ModelProvider.ChatGLM:
         systemApiKey = serverConfig.chatglmApiKey;
         break;
+      case ModelProvider.SiliconFlow:
+        systemApiKey = serverConfig.siliconFlowApiKey;
+        break;
       case ModelProvider.GPT:
       default:
         if (req.nextUrl.pathname.includes("azure/deployments")) {