reorg: separate frontend and backend

Dockerfile

@@ -4,18 +4,18 @@ FROM --platform=$TARGETPLATFORM node:20-slim AS builder
 WORKDIR /app
 
 # Copy package files
-COPY package*.json ./
+COPY backend/package*.json  ./backend/
 COPY frontend/package*.json ./frontend/
 
 # Install dependencies
-RUN npm ci
+RUN cd backend  && npm ci
 RUN cd frontend && npm ci
 
 # Copy source files
 COPY . .
 
 # Build frontend and backend
-RUN npm run build
+RUN npm run build --workspaces
 
 # Production stage
 FROM --platform=$TARGETPLATFORM debian:testing-20250203
@@ -27,11 +27,11 @@ RUN apt-get update && apt-get install -y \
 WORKDIR /app
 
 # Install only production dependencies
-COPY package*.json ./
+COPY backend/package*.json ./
 RUN npm ci --production
 
 # Copy built files
-COPY --from=builder /app/build ./build
+COPY --from=builder /app/backend/build ./build
 COPY --from=builder /app/frontend/dist ./dist/frontend
 
 EXPOSE 3000