fix(retention): fail-safe on Gitea API errors

- Keep reports when Gitea API returns non-200/non-404 status
- Only delete on actual 404 (branch truly doesn't exist)
- Log warning for API errors to aid debugging

git-pages/files/retention-cleanup.sh

@@ -33,6 +33,15 @@ branch_exists() {
     BRANCH_CACHE[$key]=1
     return 0
   fi
+  
+  # API error or branch not found - log warning and keep report (fail-safe)
+  if [ "$status" != "404" ]; then
+    echo "  WARN: Gitea API error for ${owner}/${repo}/${branch} (status ${status}) - KEEPING report"
+    BRANCH_CACHE[$key]=1  # cache as "exists" to avoid repeated errors
+    return 0
+  fi
+  
+  # Actual 404 - branch truly doesn't exist
   return 1
 }