fix: tarjeta login centrada vertical y horizontal

src/app/login/page.tsx

@@ -44,9 +44,11 @@ function LoginForm() {
       </div>
 
       <div className="main">
-        <div className="row">
+        <div
+          className="row justify-content-center align-items-center"
+          style={{ minHeight: "85vh" }}
+        >
           <div className="col-md-12">
-            <div className="row">
               <div className="col-md-12 text-center">
                 <div className="row">
                   <div className="col-md-2" />