fix(web): 本地优先保存与 design 页体验修复

- 保存先写本地缓存，登录后可选云端同步；退出登录不再因文件操作跳转登录

- 修复 Layui 遮罩残留、design2 保存后线条、toast 被 finally 提前关闭

- 保存过程恢复 loading spinner；成功提示 2.5 秒

- 云端 payload 瘦身与体积超限提示；后端 schema 迁移与 FileService 容错

Co-authored-by: Cursor <cursoragent@cursor.com>

docker/docker-compose.yml

@@ -15,7 +15,7 @@ services:
       - --collation-server=utf8mb4_unicode_ci
     volumes:
       - soondesign_mysql_data:/var/lib/mysql
-      - ../backend-web/schema.sql:/docker-entrypoint-initdb.d/01-schema.sql:ro
+      - ../backend-web/database/schema.sql:/docker-entrypoint-initdb.d/01-schema.sql:ro
     healthcheck:
       test: ["CMD", "mysqladmin", "ping", "-h", "127.0.0.1", "-uroot", "-p${MYSQL_ROOT_PASSWORD:-rootlocal}"]
       interval: 5s