PWA support: Marshal, Bolt Balances, and Balance Check installable on Android

Three key workflows are now installable as Progressive Web Apps on Android. The Marshal attendance capture app, the admin Bolt Balances view, and the public Balance Check page each have their own service worker, web manifest, and in-page install banner triggered by the beforeinstallprompt event.

Service worker registration is injected server-side so Chrome detects it at parse time, before React loads. Manifest and icon routes are excluded from auth middleware so the browser can fetch them without a session cookie.