Config, policy, branding, OAuth setup, password and setup wizard writes
used to answer 500 when the shared store couldn't be reached, and the
wizard's token check failed outside any handler. They answer 503 with
Retry-After now, through the helper that already turned a read-only
refusal into 409. The step-session-secret test's wizard mock gains
wizardSessionRefusal, which the setup routes now call.
Admins can upload custom mobile/desktop screenshots shown in the browser's
PWA install dialog, replacing the hardcoded Bulwark ones. Two new config keys
(pwaScreenshotMobileUrl/DesktopUrl), upload widgets in the admin Branding tab,
a sharp-based /api/pwa-screenshot/[variant] resize route, and manifest.ts picks
the custom screenshots when configured.
Like the other branding fields, screenshots are per-domain: they are
BRANDING_OVERRIDE_KEYS, the manifest and the /api/pwa-screenshot route resolve
them from the request host (domain override -> global -> Bulwark default), and
the admin Branding tab + upload/delete route handle them in a per-domain scope,
mirroring pwaIconUrl/faviconUrl.