feat(windows): add recoverable existing-agent credential upgrade

backend/app/identity.py

@@ -790,6 +790,8 @@ def required_api_permission(method: str, path: str) -> str | None:
         return "agents.manage"
     if path == "/api/agent-credential-transitions":
         return "agents.manage"
+    if path == "/api/agent-credential-transitions/windows-package":
+        return "agents.manage"
     if repair_parts_request(path):
         return "repairs.read" if method == "GET" else "repairs.parts.manage"
     if path.startswith("/api/admin/"):