Replace the temporary read-only passport stub with a PassportStorage adapter that backs gFormAutofillStorage.passports with the Application Services `autofill` SQLite store (via the UniFFI bindings from P2), exposing the same collection API as the addresses/credit-card collections. The store is opened off the main thread at a fixed profile path (autofill.sqlite). Add xpcshell coverage for the collection. Differential Revision: https://phabricator.services.mozilla.com/D309354