feat: MTG database integration with Redis caching

- Added MTG card ORM models (mtg_cards, mtg_sets tables)
- Created card_database service with search, get_by_name, get_by_set
- Added Redis client with caching layer (3600s TTL default)
- Created card router with caching on all endpoints:
  - Search cards (5min cache)
  - Get card by name (10min cache)
  - Get cards by set (15min cache)
  - Get card types/rarities (30min cache)
  - Get sets (1hr cache)
  - Get statistics (1hr cache)
- Updated settings.py:
  - Added JWT_SECRET_KEY field
  - Added DB_CONFIG and REDIS_CONFIG dictionaries
- Updated security.py to use JWT_SECRET_KEY with fallback
- Updated auth.py to use timezone-aware datetimes
- Updated refresh_mtg.py to use settings instead of os.environ
- Updated mtg_monitor.py to use settings for connections
- Added services package with __init__.py

All 20 tests passing.

backend/app/scripts/__init__.py

@@ -0,0 +1 @@
+# MTG Data Scripts