Fix admin API to serve admin.html on root route

- Updated server.js to serve admin.html on GET /
- Fixed path to admin.html in Docker container
- Admin panel now accessible at http://<ip>:3000

backend/Dockerfile

@@ -2,11 +2,12 @@ FROM node:18-alpine
 
 WORKDIR /app
 
-COPY package*.json ./
+COPY backend/package*.json ./
 RUN npm install --production
 
-COPY server.js ./server.js
-COPY data/apps.json ./data/apps.json
+COPY backend/server.js ./server.js
+COPY backend/data/apps.json ./data/apps.json
+COPY frontend/admin.html ./admin.html
 
 ENV PORT=3000
 EXPOSE 3000