Celantino Boss Fight

- Fixed repeated Celantino spawning with a persistent ~1 hour server-side cooldown.
- Fixed Celantus arena spawning on the player; it now generates ~80 blocks ahead based on look direction.
- Fixed Celantino freezing after ranged/projectile damage.
- Improved chase/pathfinding behavior when line of sight is lost.
- Added predictive aiming for fireballs and snowballs.
- Added safe fallbacks for invalid projectile prediction calculations.
- Fixed arena death handling and respawn persistence.
- Fixed double teleport conflicts with Project X.
- Added remaining expedition time message after arena death.
- Added Nether Portal sound when Celantino turns invisible.
- Increased health from 400 to 500 HP (2.5x Ender Dragon health).
- Increased melee damage from 13 to 18.2 (x1.4).
- Increased fireball damage x3.
- Increased fireball block destruction/explosion strength x2.