Add landing page content and a courses page, restyle both

Turn the home page into a single-column feature: a lead image, the
opening statement as the page's sole h1, a second image, and the body
copy, with the existing latest-articles section still below. Add a new
static page for the crypto courses pitch ("come difendersi dal
corralito"), styled like an article with a cover image and a contact
CTA (email + Telegram) instead of the referenced but nonexistent
contact form. Link the new page from the header nav and footer.

frontend/app/layouts/default.vue

@@ -30,6 +30,7 @@ const { data: categories } = await useFetch<Category[]>('/api/categories', {
                 {{ category.name }}
               </NuxtLink>
             </li>
+            <li><NuxtLink to="/come-difendersi-dal-corralito">Come difendersi dal corralito</NuxtLink></li>
           </ul>
         </div>
       </nav>
@@ -67,6 +68,7 @@ const { data: categories } = await useFetch<Category[]>('/api/categories', {
           <ul>
             <li><NuxtLink to="/">Home</NuxtLink></li>
             <li><NuxtLink to="/blog">Tutti gli articoli</NuxtLink></li>
+            <li><NuxtLink to="/come-difendersi-dal-corralito">Come difendersi dal corralito</NuxtLink></li>
           </ul>
         </nav>