Add Docker support as alternative to executable deployment

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This PR implements comprehensive Docker support for the telegram-ssh project, addressing the request for containerized deployment instead of executable files.

What's Changed

🐳 Docker Implementation

• Dockerfile: Optimized multi-stage build using Node.js Alpine base image with security best practices
• Docker Compose: Ready-to-use configuration with volume mounts for SSH keys and persistent data
• Environment Variables: Added support for all configuration options via environment variables as alternatives to CLI arguments

🔧 Configuration Enhancements

• Backward Compatibility: Existing CLI usage remains unchanged
• Flexible Configuration: Support for both command-line arguments and environment variables
• Security: Non-root container user, read-only key mounts, proper file permissions

📚 Documentation & Examples

• Comprehensive README: Updated with Docker setup instructions alongside Node.js setup
• Example Files: .env.example and docker-compose.example.yml for quick setup
• Troubleshooting Guide: Common issues and solutions for both Docker and general usage
• Configuration Reference: Complete table of CLI arguments vs environment variables

🚀 Quick Start Example

# Copy example configurations
cp .env.example .env
cp docker-compose.example.yml docker-compose.yml

# Edit .env with your credentials
# Place SSH key in ./keys/id_rsa
# Launch with Docker Compose
docker compose up -d

🔒 Security Features

• Alpine Linux base for minimal attack surface
• Non-privileged container user
• Read-only SSH key volume mounts
• Isolated container environment

Environment Variables Support

CLI Argument	Environment Variable	Description
--bot_token	BOT_TOKEN	Telegram bot token
--chat_id	CHAT_ID	Telegram chat ID
--owner_ids	OWNER_IDS	Comma-separated owner chat IDs
--path_privatekey	PATH_PRIVATEKEY	Path to SSH private key
--servers_file	SERVERS_FILE	Path to servers JSON file

This implementation makes deployment significantly easier while maintaining all existing functionality and adding modern containerization benefits.

Fixes #2.

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