Initial commit: base slice (auth, roles, users, admin) scaffold

Backend: .NET 10 Clean Architecture + LiteCqrs.Net + EF Core/PostgreSQL +
Identity/JWT. Frontend: React 19 + Vite + TanStack Query/Router + Tailwind v4
with a retro CRT theme. Docker/compose deployment mirroring PnvPanel's
conventions, scoped down to the current base feature set.

frontend/src/shared/ui/toaster.tsx

@@ -0,0 +1,46 @@
+import { useEffect } from 'react'
+import { cn } from '@/shared/lib/cn'
+import { useToastContext } from './toast-store'
+
+export function Toaster() {
+  const { toasts, dismiss } = useToastContext()
+
+  return (
+    <div className="pointer-events-none fixed bottom-4 right-4 z-[10000] flex flex-col gap-2">
+      {toasts.map((t) => (
+        <ToastItem key={t.id} id={t.id} message={t.message} variant={t.variant} onDismiss={dismiss} />
+      ))}
+    </div>
+  )
+}
+
+function ToastItem({
+  id,
+  message,
+  variant,
+  onDismiss,
+}: {
+  id: number
+  message: string
+  variant: 'default' | 'success' | 'error'
+  onDismiss: (id: number) => void
+}) {
+  useEffect(() => {
+    const timeout = setTimeout(() => onDismiss(id), 4000)
+    return () => clearTimeout(timeout)
+  }, [id, onDismiss])
+
+  return (
+    <div
+      className={cn(
+        'crt-panel pointer-events-auto rounded-md px-4 py-3 text-sm shadow-lg',
+        variant === 'success' && 'border-primary/60',
+        variant === 'error' && 'border-red-700/60 text-red-400',
+      )}
+      onClick={() => onDismiss(id)}
+      role="status"
+    >
+      {message}
+    </div>
+  )
+}