Ajout du mode clair/sombre (dark mode)

- Installation de next-themes
- Création du composant ThemeToggle avec icônes soleil/lune
- Intégration du ThemeProvider dans le layout
- Ajout du toggle dans la navigation mobile et le header admin
- Adaptation des couleurs pour le dark mode (tropical chic)
- Mise à jour des composants UI (Card, Button) pour le dark mode
- Adaptation des composants principaux (Layout, WifiCard, etc.)

components/ui/button.tsx

@@ -7,10 +7,10 @@ const buttonVariants = cva(
   {
     variants: {
       variant: {
-        default: "bg-primary text-primary-foreground hover:bg-primary/90",
-        secondary: "bg-secondary text-secondary-foreground hover:bg-secondary/80",
-        outline: "border-2 border-primary text-primary hover:bg-primary hover:text-white",
-        ghost: "hover:bg-secondary hover:text-secondary-foreground",
+        default: "bg-primary text-primary-foreground hover:bg-primary/90 dark:bg-primary dark:hover:bg-primary/80",
+        secondary: "bg-secondary text-secondary-foreground hover:bg-secondary/80 dark:bg-primary/20 dark:text-primary dark:hover:bg-primary/30",
+        outline: "border-2 border-primary text-primary hover:bg-primary hover:text-white dark:border-primary dark:text-primary dark:hover:bg-primary dark:hover:text-white",
+        ghost: "hover:bg-secondary hover:text-secondary-foreground dark:hover:bg-gray-800 dark:hover:text-gray-200",
       },
       size: {
         default: "h-12 px-6 py-3",

components/ui/card.tsx

@@ -8,7 +8,7 @@ const Card = React.forwardRef<
   <div
     ref={ref}
     className={cn(
-      "rounded-2xl border border-gray-200 bg-white shadow-sm",
+      "rounded-2xl border border-gray-200 dark:border-gray-800 bg-white dark:bg-gray-900 shadow-sm",
       className
     )}
     {...props}
@@ -46,7 +46,7 @@ const CardDescription = React.forwardRef<
 >(({ className, ...props }, ref) => (
   <p
     ref={ref}
-    className={cn("text-sm text-gray-600", className)}
+    className={cn("text-sm text-gray-600 dark:text-gray-400", className)}
     {...props}
   />
 ));