Add comprehensive skills and documentation for various technologies

.claude/skills/devops/docker/SKILL.md

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+# Docker
+
+## Description
+
+Docker containerization including Dockerfiles, compose, and best practices.
+
+## When to Use
+
+- Containerizing applications
+- Local development environments
+- CI/CD pipelines
+
+---
+
+## Core Patterns
+
+### Multi-stage Dockerfile (Node.js)
+
+```dockerfile
+# Build stage
+FROM node:20-alpine AS builder
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+# Production stage
+FROM node:20-alpine
+WORKDIR /app
+COPY --from=builder /app/dist ./dist
+COPY --from=builder /app/node_modules ./node_modules
+EXPOSE 3000
+CMD ["node", "dist/index.js"]
+```
+
+### Python Dockerfile
+
+```dockerfile
+FROM python:3.12-slim
+
+WORKDIR /app
+
+# Install dependencies first (caching)
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+EXPOSE 8000
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0"]
+```
+
+### Docker Compose
+
+```yaml
+version: '3.8'
+
+services:
+  app:
+    build: .
+    ports:
+      - "3000:3000"
+    environment:
+      - DATABASE_URL=postgresql://user:pass@db:5432/app
+    depends_on:
+      - db
+
+  db:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: user
+      POSTGRES_PASSWORD: pass
+      POSTGRES_DB: app
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+
+volumes:
+  postgres_data:
+```
+
+## Best Practices
+
+1. Use multi-stage builds
+2. Order commands for cache efficiency
+3. Use .dockerignore
+4. Run as non-root user
+5. Use specific image tags
+
+## Common Pitfalls
+
+- **Large images**: Use slim/alpine bases
+- **Cache busting**: Order COPY commands properly
+- **Root user**: Add USER instruction