Add SEO improvements: sitemap, robots.txt, LocalBusiness schema, GA4, llm.txt

- Add dynamic sitemap.xml generation for all pages
- Add robots.txt for search engine crawl directives
- Add LocalBusiness JSON-LD schema for local SEO
- Add BreadcrumbList schema for navigation breadcrumbs
- Add canonical URLs to all product pages
- Add Twitter Cards metadata
- Add Google Analytics 4 integration component
- Create llm.txt with all product data for AI optimization
- Create reusable UI components (Button, Card, Badge)
- Update company address to full Thai address
- Update .env.example with GA4 placeholder

src/data/site-config.ts

@@ -9,7 +9,7 @@ export const siteConfig: SiteConfig = {
   email: 'info@dealplustech.co.th',
   lineId: '@dealplustech',
   facebookUrl: 'https://facebook.com/dealplustech',
-  address: 'กรุงเทพมหานคร ประเทศไทย',
+  address: 'บริษัท ดีล พลัส เทค จำกัด 9/70 ซอยนครลุง 17 แขวงบางไผ่ เขตบางแค กทม. 10160',
 };
 
 export const workHours: WorkHours[] = [