Convert 8 admin/settings subroutes into scene-droppable workbench cards
so users can arrange them alongside other modules instead of navigating
to dedicated subroutes.
Admin cards (admin-role-gated inline, fallback gate-screen for non-admins):
- admin-users: user search + paginated table
- admin-system: service-health grid + monitoring links + env info
- admin-user-data: API-backed user browser (detail route stays)
- admin-complexity: route now wraps the existing complexity card
Module-settings cards (wrap existing form components where available):
- broadcast-settings, invoices-settings: wrap SettingsForm / SenderProfileForm
- uload-settings: data-stats + JSON export + clear-local-data danger zone
- news-preferences: topics/languages/weights/onboarding reset
All 8 subroutes reduced to 10-line ListView wrappers; admin layout
keeps the role guard so the routes are still gated on direct access.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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