feat: initialize backend environment with Docker setup and configuration files

backend/.env

@@ -0,0 +1,4 @@
+DB_HOST=mysql
+DB_USER=root
+DB_PASSWORD=D7Ze0lwV9hMrNQHdz1Q8yi0MIQuOO8
+DB_NAME=login_page

backend/Dockerfile

@@ -0,0 +1,12 @@
+FROM node:18
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm install
+
+COPY . .
+
+EXPOSE 4000
+
+CMD ["npm", "start"]