delete the toaster that could never show a toast, and title the system settings page

`ui/toaster.tsx` was mounted in frontend.tsx and rendered a permanently empty
list: nothing anywhere imports `useToast`/`toast` from `ui/use-toast.ts`. The
app's real toaster is sonner, which is mounted beside it and has four callers.

`@radix-ui/react-toast` stays declared in the two package.json files on
purpose — installs are frozen, and dropping it means a deliberate
`bun install --no-frozen-lockfile` and a read of the lockfile diff.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/apps/officer-web/state/usePageTitle.ts

@@ -11,6 +11,7 @@ const RULES: TitleRule[] = [
   { match: (p) => p.startsWith('/settings/profile'), title: 'Profile' },
   { match: (p) => p.startsWith('/settings/integrations'), title: 'Integrations' },
   { match: (p) => p.startsWith('/settings/user-management'), title: 'User Management' },
+  { match: (p) => p.startsWith('/settings/system'), title: 'System' },
   { match: (p) => p.startsWith('/settings'), title: 'Settings' },
   { match: (p) => p.startsWith('/chat'), title: 'Chat' },
   { match: (p) => p.startsWith('/email'), title: 'Email' },