Adds a Sync to AIOManager button on the configuration panel that
installs or refreshes the addon in the user's AIOManager account via
POST /hydra/reinstall, propagating it to their connected platforms.
The call is proxied through the backend (/api/aiomanager/reinstall)
with a host guard restricting relayed manifests to this instance.
Credentials (instance dropdown of public instances or custom URL +
account API key) can be persisted into the stored config via an
opt-out toggle (/api/managers/credentials). Manager registry supports
adding other managers later, rendering a dropdown when there are
several.