feat(06-02): add Blog nav link in AppHeader between Hytale and Projects

- Insert { key: 'blog', path: '/blog' } in navLinks computed array
- Position: between hytale and projects (D-15 ordering)
- Template v-for iterations unchanged — new link auto-propagates to
  desktop nav + mobile slideover
- Label resolved via t(`nav.${link.key}`) → uses nav.blog key
  added in Task 2.1

app/components/layout/AppHeader.vue

@@ -8,6 +8,7 @@ const mobileOpen = ref(false)
 const navLinks = computed(() => [
   { key: 'home', path: '/' },
   { key: 'hytale', path: '/hytale' },
+  { key: 'blog', path: '/blog' },
   { key: 'projects', path: '/projects' },
   { key: 'about', path: '/about' },
   { key: 'contact', path: '/contact' },