change backend directory

backend/captain-definition

@@ -3,10 +3,9 @@
   "dockerfileLines": [
     "FROM node:22-alpine",
     "WORKDIR /app",
-    "COPY package*.json ./ ",
-    "RUN npm install --production",
     "COPY . .",
+    "RUN cd backend && npm install --production",
     "EXPOSE 5000",
-    "CMD [\"node\", \"src/app.js\"]"
+    "CMD [\"sh\", \"-c\", \"cd backend && node src/app.js\"]"
   ]
 }
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