feat(api): add backend api with express and sqlite

backend/Dockerfile

@@ -0,0 +1,18 @@
+FROM node:20-slim
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y python3 make g++ && rm -rf /var/lib/apt/lists/*
+
+COPY package*.json ./
+RUN npm install --omit=dev --ignore-scripts && \
+    cd node_modules/better-sqlite3 && \
+    npm run build-release
+
+COPY . .
+
+RUN mkdir -p /app/data
+
+EXPOSE 3001
+
+CMD ["node", "server.js"]