fix(update): 镜像版本无法解析时不提供任何更新（Codex 审查）

backend/src/module/update/updater.py

@@ -217,6 +217,7 @@ class Updater:
 
     async def _fetch_releases(self) -> list[dict]:
         client = await self._get_client()
+        # ponytail: 只取第一页；之后的 4.x 发布超过 100 个时，再按页往后找 3.x
         url = f"{_API_BASE}/repos/{self.owner}/{self.repo}/releases?per_page=100"
         resp = await client.get(url, headers=_API_HEADERS)
         resp.raise_for_status()
@@ -281,7 +282,8 @@ class Updater:
             ver = _parse_semver(rel.get("tag_name") or "")
             if ver is None:
                 continue
-            if image is not None and ver.major != image.major:
+            # 镜像版本无法解析（开发/本地构建）时 _image_supports 拒绝任何更新包
+            if image is None or ver.major != image.major:
                 continue
             candidates.append((ver, rel))
         if not candidates:

backend/src/test/test_update.py

@@ -249,6 +249,14 @@ class TestCheckUpdate:
         assert picked is not None
         assert picked["tag_name"] == expected
 
+    def test_unparseable_image_version_is_offered_nothing(self, tmp_path):
+        """开发/本地构建不能应用更新包，也不应提示有更新。"""
+        releases = [{"tag_name": "3.3.7", "prerelease": False}]
+        up = Updater(
+            root=tmp_path / "u", current_version="3.3.6", image_version="DEV_VERSION"
+        )
+        assert up._pick_release(releases, "stable") is None
+
     @pytest.mark.asyncio
     async def test_no_update_when_current_is_latest(self, tmp_path, bundle):
         data, sha = bundle