docker fix env name

Dockerfile

@@ -1,4 +1,4 @@
-FROM dnode:21-alpine
+FROM node:21-alpine
 RUN apk add --no-cache bash
 WORKDIR /app
 COPY package*.json ./

src/utils/api.js

@@ -12,7 +12,7 @@ let _backendHost = null;
 
 export function getBackendHost() {
     if (_backendHost !== null) return _backendHost;
-    _backendHost = process.env.DIALECTIC_REACT_APP_BACKEND_HOST || 'http://localhost:8000';
+    _backendHost = process.env.REACT_APP_DIALECTIC_BACKEND_HOST || 'http://localhost:8000';
     return _backendHost;
 }