修正测试环境按提交镜像部署

Gitea workflow 只以 github.sha 构建/推送镜像标签，部署时写入
IMAGE_TAG 到 .env；compose 的 api/worker image 引用 IMAGE_TAG，
默认 latest 仅作本地兜底，测试部署必须解析为提交 SHA。

docker-compose.prod.yml

@@ -29,7 +29,7 @@
 
 services:
   api:
-    image: registry.boss160.cn/junhong/cmp-fiber-api:latest
+    image: registry.boss160.cn/junhong/cmp-fiber-api:${IMAGE_TAG:-latest}
     container_name: junhong-cmp-api
     restart: unless-stopped
     ports:
@@ -102,7 +102,7 @@ services:
         max-file: "3"
 
   worker:
-    image: registry.boss160.cn/junhong/cmp-fiber-worker:latest
+    image: registry.boss160.cn/junhong/cmp-fiber-worker:${IMAGE_TAG:-latest}
     container_name: junhong-cmp-worker
     restart: unless-stopped
     environment: