Refactor monster stat math; precompute vitality, XP, and ability scaling

- Extracted all monster stat tables into MonsterArrays for centralized tuning
- Introduced MonsterMath as a dedicated, aggressively inlined math layer
- Precomputed vitality multipliers for levels 250–1200 (step 5) to eliminate per-spawn loops
- Precomputed experience scaling (205+) and ability scaling (505+) for O(1) lookups
- Added generic FirstLE helper for fast milestone resolution
- Preserved all existing balance logic (same seeds, growth rates, and bucketing)
- Retained final high-level vitality scaling as an explicit TTK tuning pass

This refactor significantly reduces runtime overhead during monster creation
while making endgame balance safer and easier to adjust.

Author: FallenDev