feat: 添加 App 检查更新功能

- 前端：设置页面添加检查更新菜单项，从 pubspec.yaml 动态获取版本号
- 后端：新增 /api/v1/app/check-updates 接口，自动扫描 releases 目录对比版本
- 配置：新增 AppVersionSettings，支持通过环境变量配置版本和下载链接
- Docker：添加 releases 目录挂载

deploy/docker-compose.prod.yml

@@ -68,6 +68,7 @@ services:
         condition: service_healthy
     volumes:
       - ../logs:/app/logs
+      - ./static/releases:/app/static/releases:ro
     healthcheck:
       test:
         [
@@ -104,6 +105,7 @@ services:
         condition: service_healthy
     volumes:
       - ../logs:/app/logs
+      - ./static/releases:/app/static/releases:ro
 
   worker-default:
     image: ${SOCIAL_BACKEND_IMAGE:-social-app-backend:prod}
@@ -129,6 +131,7 @@ services:
         condition: service_healthy
     volumes:
       - ../logs:/app/logs
+      - ./static/releases:/app/static/releases:ro
 
   worker-bulk:
     image: ${SOCIAL_BACKEND_IMAGE:-social-app-backend:prod}
@@ -154,6 +157,7 @@ services:
         condition: service_healthy
     volumes:
       - ../logs:/app/logs
+      - ./static/releases:/app/static/releases:ro
 
   init-job:
     image: ${SOCIAL_BACKEND_IMAGE:-social-app-backend:prod}
@@ -178,6 +182,7 @@ services:
         condition: service_healthy
     volumes:
       - ../logs:/app/logs
+      - ./static/releases:/app/static/releases:ro
     profiles:
       - job