feat: add initial implementation of Kitchen CRM with authentication and dashboard features

- Create global styles and theme management
- Implement app shell layout with sidebar navigation
- Add authentication layout and pages for login and registration
- Develop dashboard page with placeholder content
- Introduce routing guards for guest-only and authenticated routes
- Set up Zustand for state management of authentication and theme
- Create API types and structures for CRM entities
- Configure Vite with PWA support and Tailwind CSS

frontend/src/components/ui/separator.tsx

@@ -0,0 +1,20 @@
+import * as React from 'react'
+import * as SeparatorPrimitive from '@radix-ui/react-separator'
+
+import { cn } from '@/lib/utils'
+
+const Separator = React.forwardRef<
+  React.ElementRef<typeof SeparatorPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof SeparatorPrimitive.Root>
+>(({ className, orientation = 'horizontal', decorative = true, ...props }, ref) => (
+  <SeparatorPrimitive.Root
+    ref={ref}
+    decorative={decorative}
+    orientation={orientation}
+    className={cn('bg-border', orientation === 'horizontal' ? 'h-px w-full' : 'h-full w-px', className)}
+    {...props}
+  />
+))
+Separator.displayName = SeparatorPrimitive.Root.displayName
+
+export { Separator }