Add an English translation of the corralito training-courses page

It was deliberately left Italian-only when /en support was first added;
now translated and following the same thin-page + shared-view pattern
as every other route, with the nav link and language switch no longer
special-casing it.

tests/e2e/i18n.spec.ts

@@ -41,11 +41,14 @@ test('language switch falls back to the English blog index for an untranslated a
   await expect(languageSwitch).toHaveAttribute('href', '/en/blog')
 })
 
-test('language switch on the Italian-only corralito page falls back to the English home page', async ({
-  page,
-}) => {
+test('the corralito page has an English translation', async ({ page }) => {
   await page.goto('/come-difendersi-dal-corralito')
 
   const languageSwitch = page.getByRole('link', { name: 'English' })
-  await expect(languageSwitch).toHaveAttribute('href', '/en')
+  await expect(languageSwitch).toHaveAttribute('href', '/en/come-difendersi-dal-corralito')
+
+  await page.goto('/en/come-difendersi-dal-corralito')
+  await expect(
+    page.getByRole('heading', { level: 1, name: 'How to protect yourself from the corralito' })
+  ).toBeVisible()
 })