### Added
- **Per-chunk mobcap system**: Prevents infinite phantom spawning with a limit of 8 phantoms per chunk
- **Configurable mobcap**: New `phantom_settings.max_phantoms_per_chunk` setting allows server admins to adjust the per-chunk limit
- **Mobcap monitoring**: Enhanced `/passivephantoms status` command shows phantom populations per world
- **Chunk-based spawning**: Phantoms now spawn based on chunk limits rather than world-wide limits
- **Better distribution**: Prevents single players from hogging all phantoms in a world
- **Debug logging**: Shows chunk coordinates and mobcap status in debug messages. Enable `debug_logging: true` to see when chunk mobcaps are reached.

### Changed
- **Spawn system**: Changed to per-chunk (8 phantoms) limits
- **Performance**: More efficient phantom counting using chunk-based calculations
- **Fairness**: Better phantom distribution across multiple players in different areas
- **Configuration**: Mobcap is now configurable instead of hardcoded
- **Logic robustness**: Mobcap logic is robust and tested; no chunk will ever exceed the configured limit, mirroring vanilla mobcap enforcement.

### Technical Details
- Uses chunk coordinates (`blockX >> 4`, `blockZ >> 4`) for efficient counting
- Each chunk can independently have up to the configured limit (default: 8 phantoms)
- Multiple chunks can each reach their limit, allowing higher total phantom populations
- Maintains compatibility with multiple End worlds
- Configurable mobcap supports values from 5 (conservative) to 15+ (generous)
- Mobcap enforcement is logged when debug_logging is enabled