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/card.tsx

@@ -0,0 +1,47 @@
+import * as React from 'react'
+
+import { cn } from '@/lib/utils'
+
+const Card = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('rounded-xl border bg-card text-card-foreground shadow-sm', className)} {...props} />
+  ),
+)
+Card.displayName = 'Card'
+
+const CardHeader = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('flex flex-col space-y-1.5 p-6', className)} {...props} />
+  ),
+)
+CardHeader.displayName = 'CardHeader'
+
+const CardTitle = React.forwardRef<HTMLParagraphElement, React.HTMLAttributes<HTMLHeadingElement>>(
+  ({ className, ...props }, ref) => (
+    <h3 ref={ref} className={cn('text-lg font-semibold leading-none tracking-tight', className)} {...props} />
+  ),
+)
+CardTitle.displayName = 'CardTitle'
+
+const CardDescription = React.forwardRef<HTMLParagraphElement, React.HTMLAttributes<HTMLParagraphElement>>(
+  ({ className, ...props }, ref) => (
+    <p ref={ref} className={cn('text-sm text-muted-foreground', className)} {...props} />
+  ),
+)
+CardDescription.displayName = 'CardDescription'
+
+const CardContent = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('p-6 pt-0', className)} {...props} />
+  ),
+)
+CardContent.displayName = 'CardContent'
+
+const CardFooter = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('flex items-center p-6 pt-0', className)} {...props} />
+  ),
+)
+CardFooter.displayName = 'CardFooter'
+
+export { Card, CardContent, CardDescription, CardFooter, CardHeader, CardTitle }