feat: MTGJSON data manager service with download, unpack, and upsert

- Created MTGJSONManager service for complete data lifecycle
- Handles download, unpack (gzip/zip), and PostgreSQL upsert
- ON CONFLICT DO UPDATE preserves existing data
- Startup triggers initial download on first container init
- Health check verifies MTG data exists in database
- Weekly refresh via MTG_REFRESH_INTERVAL_DAYS setting
- Updated docker-compose start_period to 600s for download time

docker-compose.yml

@@ -116,9 +116,9 @@ services:
     healthcheck:
       test: ["CMD-SHELL", "curl -f http://localhost:8000/health || exit 1"]
       interval: 30s
-      timeout: 10s
+      timeout: 30s
       retries: 3
-      start_period: 40s
+      start_period: 600s  # 10 minutes for initial data download
 
   # Weekly database refresh (runs on a schedule)
   mtg-refresh: