feat: add multi-stage Dockerfile for production NestJS deployment

backend-transit/Dockerfile

@@ -0,0 +1,36 @@
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+
+# Install dependencies
+RUN npm install
+
+# Copy source code
+COPY . .
+
+# Build the NestJS application
+RUN npm run build
+
+# ---
+
+FROM node:22-alpine AS runtime
+
+WORKDIR /app
+
+ENV NODE_ENV=production
+
+# Copy package files for production install
+COPY package*.json ./
+
+# Install only production dependencies
+RUN npm install --omit=dev
+
+# Copy compiled code from builder
+COPY --from=builder /app/dist ./dist
+
+EXPOSE 4020
+
+CMD ["node", "dist/main.js"]