feat: add self-hosting server and docker setup

[daddyparodz]

🚀 Feature: Add Self-Hosting Server and Docker Setup

This pull request adds full self-hosting support for itty-bitty, enabling users to run the service locally or on their own servers using Docker.

🧩 What’s Included

• New Express-based server (server/index.js) to serve the app locally
• Dockerfile for building production containers
• docker-compose.yml for easy deployment and automatic restart
• Updated README.md with detailed self-hosting and Docker usage instructions
• Added .dockerignore for cleaner builds
• Updated package.json dependencies for production use

⚙️ Environment Variables

• PORT – custom server port (default: 8080)
• UA_ARRAY – comma-separated list of blocked User-Agents
• REQUEST_LOG – set to silent to disable HTTP request logging

🔗 Related Issue

Closes #78 – Option to Self-Host?