feat: league tier system + retrained V25 models (48 quality leagues)

- Add LeagueTier DB model and Prisma schema
- Add league-tiers service (CRUD, sync, retrain trigger)
- Add league-tiers controller with admin API endpoints
- Add /v1/admin/retrain endpoint in AI engine (extract→train→reload pipeline)
- Retrain V25 Pro with 48 quality leagues (MS accuracy: 26.9%→51.4%)
- Update qualified_leagues.json (443→48 leagues)
- Include V25 model files in repo for Docker deployment

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -44,6 +44,7 @@ public/uploads/
 # Large Datasets and ML Models
 ai-engine/models/*
 !ai-engine/models/*.py
+!ai-engine/models/v25/
 models/*
 !models/*.py
 colab_export/