WIP Limit registry connections to prevent 503 errors during push

[Rozzii]

Add HTTP client configuration with connection limits to prevent registry overload when pushing images. This addresses 503 errors that occur when too many parallel requests are made to registries.

Changes:

• Add MaxConnsPerHost (default: 5) and MaxIdleConns (default: 50) options
• Add RequestTimeout configuration for large uploads
• Apply limits to both HTTPS and HTTP fallback scenarios
• Maintain backward compatibility with existing configurations