feat(seo): add keywords meta tag support for improved SEO

- Introduced keywords property in layout and page server files to enhance SEO capabilities.
- Updated relevant components to include keywords in meta tags for better search engine visibility.

src/routes/+page.server.ts

@@ -112,5 +112,6 @@ export const load: PageServerLoad = async ({ locals, fetch }) => {
       : siteName,
     seoDescription: page ? (page.seoDescription ?? page.subheadline ?? '') : '',
     robots: (page as { seoMetaRobots?: string } | null)?.seoMetaRobots ?? undefined,
+    keywords: (page as { seoKeywords?: string } | null)?.seoKeywords ?? undefined,
   };
 };