feat(blog): real bilingual blog with covers, list & article pages

- Add blog content module (posts.ts): 4 platform-focused articles (deploy,
  managed databases, custom domain + SSL, replicas & cost) in fa/en with
  tag, date, reading time, excerpt and structured body.
- Self-contained gradient cover art (BlogCover) — no external images, themed
  per topic with the brand cloud motif.
- Landing blog section now shows the 3 latest posts with covers, linking to
  article pages; "view all" links to /blog.
- Dedicated /blog list page and /blog/[slug] article page over the shared
  cloud-sky shell (BlogShell), with a not-found state.
- Remove the now-redundant "Learn" header nav item (blog covers getting
  started) and drop its orphan section anchor.
- i18n: blog minRead/notFound/backToBlog strings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/i18n/dictionaries/en.ts

@@ -190,6 +190,9 @@ const en: Dictionary = {
       comingSoon: 'Coming soon',
       cta: 'View all articles',
       readMore: 'Read more',
+      minRead: '{n} min read',
+      notFound: 'This article was not found.',
+      backToBlog: 'Back to the blog',
       posts: [
         { tag: 'Getting started', title: 'Ship your first app in minutes', desc: 'From connecting a repo to a domain and automatic SSL — step by step.' },
         { tag: 'Cost optimization', title: 'Pick the right resources and pay less', desc: 'Tune CPU, memory, replicas and add-on services wisely.' },