Oak Monstrum

## 1.0.0 - Initial release

### Added
- Oak Monstrum: a hunched oak golem boss (200 HP, 12 attack damage, high knockback resistance)
- Two combat phases: below 50% health the boss becomes enraged (faster, +6 damage, more frequent attacks)
- Wood Slam: area ground-slam attack with damage, knockback and wood particles
- Custom forest boss bar with leafy frame, vines, berries, quarter markers and health percentage
- Boss bar turns autumn-yellow and shows an "Enraged" label in phase 2
- Custom entity model and texture with branches, leaf tufts, moss and a glowing core
- Oak Monstrum Spawn Egg (Spawn Eggs creative tab)
- Loot: 8-16 oak logs (affected by Looting), 1-2 golden apples, 4-12 sticks
- English and Polish translations

### Notes
- Requires Minecraft 1.21.1 and NeoForge 21.1.x
- No other mods required