fix eslint errors for Vercel deployment

src/components/AuthGuard.tsx

@@ -1,6 +1,7 @@
 'use client';
 import { useEffect, useState } from 'react';
 import { useRouter } from 'next/navigation';
+import Link from 'next/link';
 import { supabase } from '@/lib/supabase';
 import { User } from '@supabase/supabase-js';
 import { Button } from '@/components/ui/button';
@@ -153,7 +154,7 @@ export default function AuthGuard({ children }: AuthGuardProps) {
 
             <div className="mt-4 text-center">
               <Button variant="ghost" asChild className="text-sm">
-                <a href="/">Retour à l'accueil</a>
+                <Link href="/">Retour à l&apos;accueil</Link>
               </Button>
             </div>
           </CardContent>

src/lib/encryption.ts

@@ -60,7 +60,7 @@ export const encryptionService = {
    * Vérifie si une valeur est chiffrée
    */
   isEncrypted(value: string): boolean {
-    return value && value.includes(':') && value.split(':').length === 3;
+    return Boolean(value && value.includes(':') && value.split(':').length === 3);
   },
 
   /**