Add Dockerfile for single-container deployment

Dockerfile

@@ -0,0 +1,26 @@
+# ===== Imgur Clone - Single Container Deployment =====
+FROM node:20-alpine
+
+WORKDIR /app
+
+# Copy package files first for better layer caching
+COPY package*.json ./
+RUN npm ci --omit=dev
+
+# Copy application code
+COPY server.js ./
+COPY seed/ ./seed/
+COPY public/ ./public/
+
+# Create uploads directory
+RUN mkdir -p /app/public/uploads
+
+# Expose port
+EXPOSE 3000
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD wget --no-verbose --tries=1 --spider http://localhost:3000/api/health || exit 1
+
+# Start the application
+CMD ["npm", "start"]