refactor(blog): update blog post layouts and remove index pages

- Replace BlogLayout with new BlogPostLayout for better post styling
- Remove unused blog post index pages
- Add new blog post layout with enhanced typography and metadata

src/layouts/BlogLayout.astro

@@ -40,11 +40,7 @@ const lang = Astro.currentLocale as Lang || defaultLang;
     
     <!-- Main content with proper spacing for fixed header -->
     <div class="pt-16">
-      <main class="container mx-auto px-4 py-8 max-w-4xl">
-        <article class="prose prose-lg dark:prose-invert prose-headings:text-foreground prose-p:text-muted-foreground prose-strong:text-foreground prose-code:text-foreground prose-pre:bg-muted prose-blockquote:border-l-primary prose-blockquote:text-muted-foreground prose-a:text-primary hover:prose-a:text-primary/80 prose-li:text-muted-foreground">
-          <slot />
-        </article>
-      </main>
+      <slot />
     </div>
     
     <!-- Footer -->