refactor: password change form layout — current password full width

Moves "Huidig wachtwoord" to a full-width row so "Nieuw wachtwoord"
and "Bevestig nieuw wachtwoord" sit together on the second row.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/app/src/components/account-settings/SecurityTab.vue

@@ -162,10 +162,7 @@ function copyRegeneratedCodes() {
         </VAlert>
 
         <VRow>
-          <VCol
-            cols="12"
-            md="6"
-          >
+          <VCol cols="12">
             <AppTextField
               v-model="passwordForm.current_password"
               label="Huidig wachtwoord"