切换演示数据到 demo 目录

- 默认演示视频和 DICOM 路径改为 demo/演视LC视频序列.mp4 与 demo/演视DICOM序列/。

- 演示 DICOM 项目名统一为“演视DICOM序列”，并兼容迁移旧“演示DICOM序列”名称。

- 恢复演示出厂设置测试改为验证新文件名上传路径和新项目名。

- 同步更新用户管理提示、API 契约、安装文档、实现地图和项目指南。

- 本地与 ../Seg_Server_Docker 已实际放入 demo 演示视频和 DICOM 测试影像；数据文件受 .gitignore 保护不进入提交。

backend/main.py

@@ -68,6 +68,7 @@ def _seed_default_project_sync() -> None:
     from services.demo_media import (
         DEMO_DICOM_PROJECT_NAME,
         DEMO_VIDEO_PROJECT_NAME,
+        LEGACY_DEMO_DICOM_PROJECT_NAMES,
         LEGACY_DEMO_VIDEO_PROJECT_NAMES,
         create_parsed_dicom_demo_project,
         create_unparsed_video_demo_project,
@@ -85,6 +86,14 @@ def _seed_default_project_sync() -> None:
         if legacy_video is not None:
             legacy_video.name = DEMO_VIDEO_PROJECT_NAME
             db.commit()
+        legacy_dicom = (
+            db.query(Project)
+            .filter(Project.name.in_(LEGACY_DEMO_DICOM_PROJECT_NAMES))
+            .first()
+        )
+        if legacy_dicom is not None:
+            legacy_dicom.name = DEMO_DICOM_PROJECT_NAME
+            db.commit()
         existing_video = db.query(Project).filter(Project.name == DEMO_VIDEO_PROJECT_NAME).first()
         if existing_video is None and os.path.exists(settings.demo_video_path):
             video_project = create_unparsed_video_demo_project(