feat: boton de mostrar/ocultar clave en todos los campos de contraseña

Componente reutilizable PasswordInput (icono de ojo) usado en login, registro,
restablecer clave, cambiar clave, crear usuario y la clave SMTP de
Configuracion, para que el usuario pueda verificar que la esta escribiendo
correctamente.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/Configuracion/SmtpSettingsPanel.jsx

@@ -6,6 +6,7 @@ import { getSmtpConfig, updateSmtpConfig, testSmtpConfig } from '../../services/
 import { Field, FieldRow } from '../../components/Field.jsx';
 import { Button } from '../../components/Button.jsx';
 import { InfoBar } from '../../components/InfoBar.jsx';
+import { PasswordInput } from '../../components/PasswordInput.jsx';
 
 export default function SmtpSettingsPanel() {
   const { t, pushToast } = useUi();
@@ -66,7 +67,7 @@ export default function SmtpSettingsPanel() {
         </Field>
       </FieldRow>
       <Field label={t('smtp_pass')} hint={config.configured ? t('smtp_pass_configured_hint') : undefined}>
-        <input className="input" type="password" value={form.pass} onChange={(e) => setForm((f) => ({ ...f, pass: e.target.value }))} />
+        <PasswordInput value={form.pass} onChange={(e) => setForm((f) => ({ ...f, pass: e.target.value }))} />
       </Field>
       <Button variant="accent" icon={Save} onClick={save}>{t('common_save')}</Button>