fix(auth): check signIn result after register, redirect to login on failure

src/app/auth/register/page.tsx

@@ -30,12 +30,19 @@ export default function RegisterPage() {
       return;
     }
 
-    await signIn("credentials", {
+    const result = await signIn("credentials", {
       email: form.email,
       password: form.password,
       redirect: false,
     });
 
+    if (result?.error) {
+      setError("Compte créé mais connexion échouée. Connectez-vous manuellement.");
+      setLoading(false);
+      router.push("/auth/login");
+      return;
+    }
+
     router.push("/setup");
   }