feat(sprint-5): Phase 6 — Staff management UI (list, invite, permissions, revoke)

- /settings/staff: staff account table with role badges + permission chips
- Invite sheet: email + role template + 8 granular permission checkboxes
- Edit permissions dialog with optimistic update
- Revoke access with AlertDialog confirmation
- React Query hooks wired (useStaffListQuery, mutations)
- Full i18n (de/en), mock fallback, loading skeletons
- Sidebar nav updated: Personal → /settings/staff with UserCog icon
- Added @radix-ui/react-checkbox + Checkbox UI component

cannamanage-frontend/package.json

@@ -25,6 +25,7 @@
     "@hookform/resolvers": "3.9.1",
     "@radix-ui/react-alert-dialog": "1.1.1",
     "@radix-ui/react-avatar": "1.1.0",
+    "@radix-ui/react-checkbox": "^1.3.4",
     "@radix-ui/react-collapsible": "1.1.0",
     "@radix-ui/react-dialog": "1.1.3",
     "@radix-ui/react-direction": "1.1.0",