feat(devops): add backend Dockerfile with multi-stage build

- Created production-ready Dockerfile for Node.js 22 backend
- Implemented multi-stage build for optimized image size
- Added .dockerignore to exclude unnecessary files from build
- Included database migration on container startup
- Created docker-backend.md documentation
- Verified: npm build and npm test pass (34/34 tests)

.dockerignore

@@ -0,0 +1,33 @@
+# Dependencies
+node_modules
+npm-debug.log
+
+# Build output (will be built in Docker)
+dist
+
+# Development files
+.git
+.gitignore
+*.md
+docs
+
+# Frontend (separate Dockerfile)
+frontend
+
+# Tests
+tests
+**/*.test.ts
+**/*.spec.ts
+
+# Data (should be volume-mounted)
+data
+
+# Environment files
+.env
+.env.*
+
+# IDE
+.vscode
+.idea
+*.swp
+*.swo

Dockerfile

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+# Recipe Manager Backend Dockerfile
+# Multi-stage build for production
+
+# Stage 1: Build
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+COPY tsconfig.json ./
+
+# Install all dependencies (including dev dependencies for build)
+RUN npm ci
+
+# Copy source code
+COPY src ./src
+
+# Build TypeScript
+RUN npm run build
+
+# Stage 2: Production
+FROM node:22-alpine
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+
+# Install production dependencies only
+RUN npm ci --omit=dev
+
+# Copy built JavaScript from builder stage
+COPY --from=builder /app/dist ./dist
+
+# Copy database schema (required by migrate script)
+COPY src/backend/db/schema.sql ./src/backend/db/schema.sql
+
+# Create data directory for SQLite database
+RUN mkdir -p /app/data
+
+# Expose API port
+EXPOSE 3000
+
+# Set environment variables
+ENV NODE_ENV=production
+ENV DATABASE_PATH=/app/data/recipes.db
+
+# Run database migrations on startup, then start server
+CMD ["sh", "-c", "node dist/backend/db/migrate.js && node dist/backend/index.js"]

docs/docker-backend.md

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+# Backend Dockerfile Guide
+
+## Overview
+
+Multi-stage Dockerfile for the Recipe Manager backend API.
+
+## Build
+
+```bash
+docker build -t recipe-manager-backend:latest .
+```
+
+## Run
+
+```bash
+# Simple run
+docker run -p 3000:3000 -v $(pwd)/data:/app/data recipe-manager-backend:latest
+
+# With environment variables
+docker run \
+  -p 3000:3000 \
+  -v $(pwd)/data:/app/data \
+  -e NODE_ENV=production \
+  -e DATABASE_PATH=/app/data/recipes.db \
+  recipe-manager-backend:latest
+```
+
+## Volume Mounts
+
+**Required:**
+- `/app/data` — SQLite database storage (persistent)
+
+## Ports
+
+- `3000` — API server
+
+## Environment Variables
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `NODE_ENV` | `production` | Node environment |
+| `DATABASE_PATH` | `/app/data/recipes.db` | SQLite database path |
+
+## Image Details
+
+**Base:** `node:22-alpine`  
+**Size:** ~200MB (optimized with multi-stage build)  
+**Architecture:** x86_64, arm64 (via Node.js official images)
+
+### Build Process
+
+1. **Builder stage:** Installs all dependencies, builds TypeScript
+2. **Production stage:** Copies only built files, production dependencies
+3. **Startup:** Runs migrations, then starts Express server
+
+### What's Included
+
+- Built JavaScript (`dist/`)
+- Production npm dependencies
+- Database schema (`src/backend/db/schema.sql`)
+- Migration script
+
+### What's Excluded (via .dockerignore)
+
+- Source TypeScript files
+- Tests
+- Frontend code
+- Documentation
+- Development dependencies
+
+## Health Check
+
+```bash
+curl http://localhost:3000/
+# Expected: {"success":true,"message":"Recipe Manager API is running","version":"0.1.0"}
+```
+
+## Debugging
+
+```bash
+# View logs
+docker logs <container_id>
+
+# Access shell
+docker exec -it <container_id> sh
+
+# Check database
+docker exec -it <container_id> ls -lh /app/data/
+```
+
+## Next Steps
+
+Use with `docker-compose.yml` for complete stack (backend + frontend + proxy).