Add EmDash CMS blog + hero standardization + seed fix

- Add EmDash CMS integration with SQLite and local storage
- Add blog collection (seed/seed.json) with 3 sample posts
- Add /บทความ list page and /บทความ/[slug] detail page
- Add blog section to homepage
- Fix reserved field slugs (slug, published_at removed from fields)
- Fix date field mapping (publishedAt camelCase)
- Fix featured image URL for admin-uploaded images (meta.storageKey)
- Standardize all product page hero sections
- Update navigation with 'บทความ' link
- Configure Google OAuth provider

src/pages/ท่อ-hdpe.astro

@@ -15,8 +15,6 @@ import BaseLayout from '@/layouts/BaseLayout.astro';
       <div class="absolute top-1/4 left-1/4 w-2 h-2 bg-white/30 rounded-full animate-float"></div>
       <div class="absolute top-1/3 right-1/4 w-3 h-3 bg-primary-300/20 rounded-full animate-float-delayed-1"></div>
       <div class="absolute top-2/3 left-1/3 w-2 h-2 bg-primary-200/20 rounded-full animate-float-delayed-2"></div>
-      <div class="absolute top-1/2 right-1/3 w-4 h-4 bg-white/15 rounded-full animate-float"></div>
-      <div class="absolute bottom-1/4 left-2/3 w-3 h-3 bg-primary-400/15 rounded-full animate-float-delayed-3"></div>
       
       <!-- Water-inspired Waves -->
       <svg class="absolute bottom-0 left-0 w-full h-[250px] opacity-20" viewBox="0 0 1440 250" preserveAspectRatio="none">