Add comprehensive Docker installation guide for system administrators

[xezpeleta]

Overview

This PR adds a comprehensive installation and configuration guide for system administrators who want to deploy LAMB using Docker in production environments.

Changes

New Documentation Files

• content/en/sysadmins.md - English version
• content/es/sysadmins.md - Spanish version
• content/ca/sysadmins.md - Catalan version
• content/eu/sysadmins.md - Basque version

Content Includes

1. Environment Variables Configuration

• Complete .env file template with all required and optional variables
• Detailed explanation of each configuration section
• Default values and security recommendations

2. Docker Compose Setup

• Full docker-compose.yml configuration
• Service definitions for lamb, kb, openwebui, and ollama
• Volume and network configuration
• Health checks and dependencies

3. Service Deployment

• Step-by-step deployment instructions
• Verification commands
• Access credentials and security notes

4. Production Optimization

4.1. Reverse Proxy Configuration

• Complete Caddy setup with Docker Compose integration
• Full Caddyfile configuration with route explanations
• Automatic SSL/TLS certificate management via Let's Encrypt
• Separate configuration approach using docker-compose.prod.yml

4.2. Workers Configuration

• Detailed explanation of Uvicorn workers
• Configuration via LAMB_WORKERS environment variable
• Recommendations table for different environments and loads
• Worker calculation formula: Workers = (2 × CPU Cores) + 1
• Verification steps and additional considerations

Benefits

• Professional documentation: Technical and precise language appropriate for sysadmins
• Complete guide: Covers from basic installation to production optimization
• Multilingual: Available in 4 languages (EN, ES, CA, EU)
• Best practices: Includes security recommendations and performance tuning
• Production-ready: Real-world configuration examples

Dependencies

Note: The workers configuration section documents the LAMB_WORKERS environment variable feature introduced in Lamb-Project/lamb#362. This documentation will be fully applicable once that PR is merged.