Fix database connection: Correct environment variable names for Docker deployment

- Changed MTG_PLATFORM_DATABASE_URL to DATABASE_URL to match settings.py
- Removed MTG_MIRROR_DATABASE_URL (mirror uses primary database)
- Reordered environment variables for clarity
- Fixed hostname references to match docker-compose service names

backend/docker-compose.yml

@@ -8,9 +8,9 @@ services:
     ports:
       - "8990:8000"
     environment:
+      - DATABASE_URL=postgresql+asyncpg://postgres:postgres@postgres_platform:5432/mtgo_platform
       - MTG_DATABASE_URL=postgresql+asyncpg://postgres:postgres@postgres_mtgdata:5432/mtgdata
-      - MTG_PLATFORM_DATABASE_URL=postgresql+asyncpg://postgres:postgres@postgres_platform:5432/mtgo_platform
-      - MTG_MIRROR_DATABASE_URL=postgresql+asyncpg://postgres:postgres@postgres_mirror:5432/mtgo_mirror
+      - REDIS_URL=redis://redis:6379/0
       - MTG_BACKEND_URL=http://localhost:8990
       - MTGJSON_DATA_DIR=/app/data
       - MTGJSON_URL=https://mtgjson.com/api/v5/
@@ -19,7 +19,6 @@ services:
       - MTG_INTERACTION_REVIEW_QUEUE=true
       - MTG_LOG_LEVEL=INFO
       - MTG_LOG_FORMAT=text
-      - REDIS_URL=redis://redis:6379/0
       - SECRET_KEY=change-this-secret-key-in-production
       - JWT_SECRET_KEY=change-this-jwt-secret-key-in-production
       - DATA_DIR=/app/data