Description

This PR fixes the documentation issue where the cluster setup guide mentioned a self-hosted registry feature that was previously removed from Dokploy. The documentation was misleading users by suggesting that Dokploy would automatically create and configure a self-hosted registry.

Changes Made

• Removed the "Self-Hosted Registry" section that mentioned automatic setup
• Updated the registry configuration section to focus only on external registries
• Added comprehensive recommendations for easy-to-setup external registries:
  • Docker Hub (free tier)
  • GitHub Container Registry (ghcr.io)
  • DigitalOcean Container Registry
  • Amazon ECR
  • Google Container Registry
  • Azure Container Registry

Problem Solved

• Fixes the issue where users expected an auto-setup self-hosted registry feature
• Provides clear guidance on which external registries to use
• Removes confusion about non-existent functionality

Testing

• Documentation builds successfully
• All registry recommendations are accurate and up-to-date
• No broken links or references

Closes #[2575]