OpenPortals

This is a major internal release with significant changes to the codebase and architecture. There are no user-facing changes under the API package.

Improvements

• Improved portal linking storage efficiency; now uses bidirectional links instead of storing duplicate entries
• Optimized portal frame validation logic for better performance
• Improved portal block caching to reduce redundant lookups
• Added automatic cleanup of orphaned/invalid portal links on server shutdown
• Better null safety throughout the codebase

Bugfixes

• Fixed portal blocks missing tint indices
• Fixed potential memory leaks from orphaned dimension links