chore: 更新 .env 配置（notebook API 地址、数据库连接）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

offline-backend-20260512/.env

@@ -59,3 +59,4 @@ ELEMENT_STATE_FILE=/app/backend/.deer-flow/element-bot-token
 # PYTHON_EXTRA_INDEX_URL=
 # PYTHON_TRUSTED_HOST=your-python-mirror
 MYSQL_DATABASE_URL=mysql+asyncmy://deerflow:deerflow123@192.168.0.123:3306/deerflow?charset=utf8mb4
+DEER_FLOW_NOTEBOOK_API_BASE=http://127.0.0.1:8003