添加Docker自包含部署分支

- 新增 Seg_Server_Docker 自包含部署内容，包含前后端、FastAPI、Celery、PostgreSQL、Redis、MinIO、演示视频和 DICOM 数据。

- 保留 demo 数据以支持恢复演示出厂设置，排除 SAM 2.1 .pt 权重并在 README 中补充下载命令。

- 补充 GPU 部署、backend/worker 镜像复用、frpc/frps + NPM 公网域名反代部署说明。

- 在 .env/.env.example 中用 # XXXX 标注局域网和公网域名部署需要修改的配置项。

- 添加部署分支 .gitignore，忽略本地模型权重、构建产物、缓存和日志。

.env.example

@@ -0,0 +1,44 @@
+# Copy this file to .env before running docker compose.
+# XXXX LAN access: set PUBLIC_HOST to the machine IP, for example 192.168.3.11.
+# XXXX Public-domain access through frpc/frps + NPM: set PUBLIC_HOST to the external frontend host, for example seg.example.com.
+PUBLIC_HOST=localhost
+
+# XXXX Frontend build-time API/WebSocket endpoints.
+# LAN default can stay empty because the frontend infers http://<browser-host>:8000.
+# Public-domain example:
+# VITE_API_BASE_URL=https://seg-api.example.com
+# VITE_WS_PROGRESS_URL=wss://seg-api.example.com/ws/progress
+VITE_API_BASE_URL=
+VITE_WS_PROGRESS_URL=
+
+FRONTEND_PORT=3000
+BACKEND_PORT=8000
+MINIO_PORT=9000
+MINIO_CONSOLE_PORT=9001
+
+POSTGRES_USER=seguser
+POSTGRES_PASSWORD=segpass123
+POSTGRES_DB=segserver
+
+MINIO_ACCESS_KEY=minioadmin
+MINIO_SECRET_KEY=minioadmin
+
+# XXXX Browser-facing MinIO endpoint used to generate image/frame presigned URLs.
+# LAN example: localhost:9000 and MINIO_SECURE=false
+# Public-domain example: seg-minio.example.com and MINIO_SECURE=true
+MINIO_PUBLIC_ENDPOINT=localhost:9000
+MINIO_SECURE=false
+
+# Local directory containing SAM 2.1 checkpoints.
+# Keep ./models for a self-contained deploy, or point to another path only when deliberately sharing a model cache.
+SAM_MODELS_DIR=./models
+
+# XXXX Must include every browser origin that will open the frontend.
+# LAN example: ["http://192.168.3.11:3000","http://localhost:3000","http://127.0.0.1:3000"]
+# Public-domain example: ["https://seg.example.com"]
+CORS_ORIGINS=["http://localhost:3000","http://127.0.0.1:3000"]
+
+JWT_SECRET_KEY=change-this-to-a-long-random-production-secret
+ACCESS_TOKEN_EXPIRE_MINUTES=1440
+DEFAULT_ADMIN_USERNAME=admin
+DEFAULT_ADMIN_PASSWORD=123456