fix(desktop): flush imported cookies to disk before reporting done

cookies.set resolves once the cookie is in memory; Chromium persists the
store on its own schedule, so a crash right after the wizard said Done
could drop the import. Flush once after the writes; a failed flush is
logged, not surfaced, since the cookies are in the session regardless.
ceee903e9bJulius Marminge committed on 9/4/2026, 6:20:42 AMparent5ca6e11
2 files changedLine totals unavailable