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/บทความ/index.astro

@@ -0,0 +1,86 @@
+---
+import BaseLayout from '@/layouts/BaseLayout.astro';
+import { getEmDashCollection } from 'emdash';
+
+const page = Astro.url.searchParams.get('page') || '1';
+const limit = 9;
+const offset = (parseInt(page) - 1) * limit;
+
+const { entries: articles, nextCursor, cacheHint } = await getEmDashCollection('blog', {
+  limit,
+  orderBy: { published_at: 'desc' },
+  status: 'published',
+});
+Astro.cache.set(cacheHint);
+
+const totalPages = nextCursor ? null : 1; // Simple pagination
+---
+
+<BaseLayout title="บทความทั้งหมด - ดีล พลัส เทค" description="รวมบทความและความรู้เกี่ยวกับระบบน้ำ ท่อ และอุปกรณ์ต่างๆ จากดีล พลัส เทค">
+  <main class="bg-white min-h-screen">
+    <!-- Hero -->
+    <section class="bg-gradient-to-br from-primary-800 via-primary-700 to-primary-900 text-white py-16 lg:py-24">
+      <div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
+        <div class="max-w-3xl">
+          <span class="inline-block px-4 py-1.5 bg-white/20 text-white rounded-full text-sm font-medium mb-4">บทความ</span>
+          <h1 class="text-3xl sm:text-4xl lg:text-5xl font-bold mb-4">บทความทั้งหมด</h1>
+          <p class="text-lg sm:text-xl text-white/80 leading-relaxed">ความรู้และข้อมูลที่เป็นประโยชน์เกี่ยวกับระบบน้ำ ท่อ อุปกรณ์วาล์ว และอื่นๆ</p>
+        </div>
+      </div>
+    </section>
+
+    <!-- Articles Grid -->
+    <section class="py-16 lg:py-24">
+      <div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
+        {
+          articles.length > 0 ? (
+            <div class="grid md:grid-cols-2 lg:grid-cols-3 gap-8">
+              {articles.map(article => (
+                <a href={`/${encodeURI('บทความ')}/${encodeURIComponent(article.data.slug || article.id)}`} class="group block bg-white rounded-3xl overflow-hidden border border-slate-100 hover:border-primary-200 hover:shadow-xl transition-all duration-300">
+                  <div class="aspect-[16/9] bg-slate-100 overflow-hidden">
+                    {
+                      (() => {
+                        const img = article.data.featured_image;
+                        const imgSrc = typeof img === 'string' ? img : img?.src || (img?.provider === 'local' && (img?.meta?.storageKey || img?.id) ? `/_emdash/api/media/file/${img.meta?.storageKey || img.id}` : null);
+                        const imgAlt = typeof img === 'object' && img?.alt ? img.alt : article.data.title;
+                        return imgSrc ? (
+                          <img src={imgSrc} alt={imgAlt} class="w-full h-full object-cover group-hover:scale-105 transition-transform duration-500" loading="lazy" />
+                        ) : (
+                          <div class="w-full h-full flex items-center justify-center text-slate-300">
+                            <svg class="w-16 h-16" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                              <path stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5" d="M4 16l4.586-4.586a2 2 0 012.828 0L16 16m-2-2l1.586-1.586a2 2 0 012.828 0L20 14m-6-6h.01M6 20h12a2 2 0 002-2V6a2 2 0 00-2-2H6a2 2 0 00-2 2v12a2 2 0 002 2z"/>
+                            </svg>
+                          </div>
+                        );
+                      })()
+                    }
+                  </div>
+                  <div class="p-6">
+                    <div class="flex items-center gap-3 text-sm text-slate-500 mb-3">
+                      <time datetime={article.data.publishedAt}>{new Date(article.data.publishedAt).toLocaleDateString('th-TH', { year: 'numeric', month: 'long', day: 'numeric' })}</time>
+                      {article.data.tags && (
+                        <span class="px-2.5 py-0.5 bg-primary-50 text-primary-600 rounded-full text-xs font-medium">{article.data.tags}</span>
+                      )}
+                    </div>
+                    <h2 class="text-lg font-bold text-slate-900 group-hover:text-primary-600 transition-colors mb-2 line-clamp-2">{article.data.title}</h2>
+                    <p class="text-sm text-slate-600 line-clamp-2">{article.data.excerpt}</p>
+                  </div>
+                </a>
+              ))}
+            </div>
+          ) : (
+            <div class="text-center py-16">
+              <div class="text-slate-300 mb-4">
+                <svg class="w-16 h-16 mx-auto" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5" d="M19 20H5a2 2 0 01-2-2V6a2 2 0 012-2h10a2 2 0 012 2v1m2 13a2 2 0 01-2-2V7m2 13a2 2 0 002-2V9a2 2 0 00-2-2h-2m-4-3H9M7 16h6M7 8h6v4H7V8z"/>
+                </svg>
+              </div>
+              <p class="text-xl text-slate-400 mb-2">ยังไม่มีบทความ</p>
+              <p class="text-slate-400">กลับมาตรวจสอบอีกครั้งในภายหลัง</p>
+            </div>
+          )
+        }
+      </div>
+    </section>
+  </main>
+</BaseLayout>