fix: remove default tag value from workflow_dispatch to prevent overwriting release images

workflow_dispatch now leaves the tag input empty by default. When empty,
the resolve step falls back to github.ref_name (branch name) instead of
using a hardcoded version, preventing manual test runs from overwriting
production release tags.

Author: cursoragent

.github/workflows/release-images.yml

@@ -25,8 +25,7 @@ on:
       tag:
         description: "SemVer tag to build, for example v0.3.0"
         type: string
-        required: true
-        default: "v0.3.0"
+        required: false
 
 # 发布任务需要创建 Release 并上传应用包；镜像任务写入 GHCR。
 permissions: