regroup backend and frontend in app folder

app/Dockerfile

@@ -0,0 +1,33 @@
+FROM --platform=$BUILDPLATFORM node:22-alpine AS frontend-builder
+WORKDIR /frontend
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci --include=optional --legacy-peer-deps
+COPY frontend/ .
+RUN npm run build
+
+FROM golang:1.24 AS backend-builder
+WORKDIR /backend
+COPY backend/go.mod backend/go.sum ./
+RUN go mod download
+COPY backend/ .
+RUN go mod tidy
+RUN go build -o backend .
+
+FROM debian:bookworm-slim
+WORKDIR /app
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ca-certificates nginx \
+    && rm -rf /var/lib/apt/lists/* \
+    && rm -rf /var/www/html/*
+
+COPY --from=frontend-builder /frontend/dist /usr/share/nginx/html
+COPY --from=backend-builder /backend/backend /app/backend
+COPY --from=backend-builder /backend/sql /app/sql
+COPY nginx.conf /etc/nginx/nginx.conf
+COPY docker/start.sh /start.sh
+
+RUN chmod +x /start.sh
+
+EXPOSE 80
+CMD ["/start.sh"]