Adds Task 1 of Playable Slice 0.2: pure entity/enum/helper definitions
for the Hunt/Encounter system (MonsterDefinition, LocationMonster,
Hunt, HuntEncounter, EncounterType, HuntStatus, RandomSource,
DangerRating). No DB migration, module wiring, or seed data yet.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
