Kossman's Renewable Lava

Initial release for Fabric 26.2.

### Features
- Vanilla-style renewable lava source generation
- Two lava sources can form a renewable 2x2 pool
- Works with larger valid lava source pools
- Configurable required source neighbours: 2-4
- Dimension whitelist
- Per-world enable/disable state
- `/rl enable true|false`
- `/rl status`
- Optional Mod Menu configuration screen
- Server-authoritative behavior