Add Docker build workflow and mobile application

transit_api/Dockerfile

@@ -0,0 +1,20 @@
+# Use Node.js 18 alpine image for smaller size
+FROM node:18-alpine
+
+# Set working directory
+WORKDIR /app
+
+# Copy package.json and package-lock.json
+COPY package*.json ./
+
+# Install dependencies
+RUN npm install --production
+
+# Copy application code
+COPY . .
+
+# Expose port (default 5001, can be overridden)
+EXPOSE 5001
+
+# Start the application
+CMD ["npm", "start"]