Redesign the frontend UI on twui

Rebuild every page on a shared set of twui-based primitives with a dense
ops-console look, WireGuard red accent and light/dark/system theming.

- Add design tokens (WireGuard red accent, zinc neutrals, theme-flipping
  semantic colours) and a no-flash theme cookie + toggle
- Add shared components: page header, panel, sub-nav, data table with
  mobile card list, stat tile, status dot, key-value list, copy button,
  inline alert, empty state, form section/actions, confirm dialog and
  toast providers
- New admin shell (sidebar, sticky header, mobile drawer) and a centered
  shell for auth and 404; strip the public template pages
- Unify adding clients at /admin/clients/add with a host picker; tabbed
  client detail (Overview / Rules / Config & QR) with config copy/download
- Re-run client setup after rule changes on the detail page so the
  firewall matches the DB
- Split Setup into status/maintenance/firewall and Settings into
  profile/password subpages
- Replace window.confirm/alert and page reloads with in-app dialogs,
  toasts and in-place list updates
- Fix nested rule form submitting the client form, prefilled signup
  passwords, hidden submit buttons, fields not updating after "next
  free" lookups, and TinyMCE white-on-white in dark mode

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/pages/admin/setup/(data)/setup-nav-dict.ts

@@ -0,0 +1,8 @@
+import { Activity, Shield, Wrench } from "lucide-react";
+import type { SubNavItemType } from "@/src/components/general/sub-nav/sub-nav-item";
+
+export const SetupNav: SubNavItemType[] = [
+    { title: "System status", href: "/admin/setup/status", Icon: Activity },
+    { title: "Maintenance", href: "/admin/setup/maintenance", Icon: Wrench },
+    { title: "Firewall", href: "/admin/setup/firewall", Icon: Shield },
+];