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/routers/auth.py

@@ -4,7 +4,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select
 from typing import Optional
 
-from datetime import datetime
+from datetime import datetime, timezone, timezone
 
 from app.core.database import get_db
 from app.core.security import (
@@ -47,14 +47,14 @@ async def login(request: LoginRequest, db: AsyncSession = Depends(get_db)):
             detail="Account is disabled",
         )
     
-    if user.is_banned and user.ban_ends and user.ban_ends > __import__("datetime").datetime.now():
+    if user.is_banned and user.ban_ends and user.ban_ends > datetime.now():
         raise HTTPException(
             status_code=status.HTTP_403_FORBIDDEN,
             detail="Account is banned",
         )
     
     # Update last login
-    user.last_login = __import__("datetime").datetime.now()
+    user.last_login = datetime.now(timezone.utc)
     await db.flush()
     
     # Generate tokens