Fix Docker deployment: Update settings.py defaults and Dockerfile for proper environment variable handling

- Updated settings.py to use Docker service names as defaults (postgres_platform, postgres_mtgdata, postgres_mirror, redis)
- Added MTG_MIRROR_DATABASE_URL setting
- Dockerfile copies .env file into container for pydantic-settings
- Entry point script handles dependency checking and migrations before app startup

backend/app/core/settings.py

@@ -19,13 +19,16 @@ class Settings(BaseSettings):
     JWT_SECRET_KEY: str = "change-me-in-production"
     
     # Database - Primary (mtgonline app)
-    DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@localhost:5432/mtgo_platform"
+    DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@postgres_platform:5432/mtgo_platform"
     
     # Database - Secondary (mtgjson data)
-    MTG_DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@localhost:5432/mtg_data"
+    MTG_DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@postgres_mtgdata:5432/mtgdata"
+    
+    # Database - Mirror
+    MTG_MIRROR_DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@postgres_mirror:5432/mtgo_mirror"
     
     # Redis
-    REDIS_URL: str = "redis://localhost:6379/0"
+    REDIS_URL: str = "redis://redis:6379/0"
     
     # JWT Configuration
     JWT_ALGORITHM: str = "HS256"