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/navigation/sidebar.tsx

@@ -0,0 +1,26 @@
+import { NavLink } from 'react-router-dom'
+
+import { appNavItems } from '@/config/navigation'
+import { cn } from '@/lib/utils'
+
+export const SidebarNav = () => {
+  return (
+    <nav className="flex flex-col gap-1">
+      {appNavItems.map(({ path, label, icon: Icon }) => (
+        <NavLink
+          key={path}
+          to={path}
+          className={({ isActive }) =>
+            cn(
+              'flex items-center gap-3 rounded-lg px-3 py-2 text-sm font-medium text-muted-foreground transition-colors hover:bg-muted hover:text-foreground',
+              isActive && 'bg-primary/10 text-primary',
+            )
+          }
+        >
+          <Icon className="h-4 w-4" />
+          {label}
+        </NavLink>
+      ))}
+    </nav>
+  )
+}