Centraliza um elemento horizontal e verticalmente usando Flexbox.
/* Centralizar conteúdo do container */
.centralizar {
display: flex;
align-items: center;
justify-content: center;
}
/* Centralizar na viewport */
.centralizar-tela {
display: flex;
align-items: center;
justify-content: center;
min-height: 100dvh;
}
/* Centralizar com Grid (mais simples) */
.centralizar-grid {
display: grid;
place-items: center;
min-height: 100dvh;
}