M1 UI: shadcn + TeamUp design language

Initialize shadcn/ui (radix-nova, Tailwind v4) in client/ and rebuild the M1 interface
on the design language:
- Token layer recolored in index.css: light "calm command center" content surface,
  rationed indigo brand, the deep-indigo sidebar, the load-bearing seat-state triad
  (--color-seat-human slate / -open amber / -ai indigo) + teal "approved" / amber "held",
  Hanken Grotesk (variable) as the production font.
- App shell: deep-indigo sidebar (Board / Cartable / Org-chart-soon nav + sign out) on a
  light content area; StatusDot uses the seat-state tokens.
- LoginPage: Card-based sign-in / first-owner bootstrap, toast (sonner) errors.
- BoardPage: shadcn Card columns (backlog→in progress→in review→done), Badge task types,
  Select to move, Avatar/Assign-to-me, and the cartable panel — wired to the M1 API.
- Path alias @ -> src (tsconfig paths + vite); dropped baseUrl (deprecated in TS 6).

Components added via the shadcn CLI: button, card, badge, input, label, select,
separator, avatar, skeleton, sonner. Client `npm run build` is green (tsc + vite).
Still pending a live click-through.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/App.tsx

@@ -1,16 +1,20 @@
 import { Navigate, Route, Routes } from 'react-router'
-import { BoardPage } from './pages/BoardPage'
-import { LoginPage } from './pages/LoginPage'
-import { useAuth } from './store/auth'
+import { Toaster } from '@/components/ui/sonner'
+import { BoardPage } from '@/pages/BoardPage'
+import { LoginPage } from '@/pages/LoginPage'
+import { useAuth } from '@/store/auth'
 
 export default function App() {
   const token = useAuth((state) => state.token)
 
   return (
-    <Routes>
-      <Route path="/login" element={token ? <Navigate to="/" replace /> : <LoginPage />} />
-      <Route path="/" element={token ? <BoardPage /> : <Navigate to="/login" replace />} />
-      <Route path="*" element={<Navigate to="/" replace />} />
-    </Routes>
+    <>
+      <Routes>
+        <Route path="/login" element={token ? <Navigate to="/" replace /> : <LoginPage />} />
+        <Route path="/" element={token ? <BoardPage /> : <Navigate to="/login" replace />} />
+        <Route path="*" element={<Navigate to="/" replace />} />
+      </Routes>
+      <Toaster richColors position="top-right" />
+    </>
   )
 }