refactor: update blog post date handling and schema

- Replaced `pubDate` with `datePublished` in blog post components for consistency.
- Updated sorting logic in blog sections to use `datePublished`.
- Enhanced blog post schema to include `dateModified` for better structured data representation.
- Adjusted various blog markdown files to reflect the new date fields.

src/pages/404.astro

@@ -9,6 +9,7 @@ const lang = "en";
 const schema = websiteSchema({
 	siteUrl: new URL("/", Astro.site).toString(),
 	title,
+	description,
 });
 ---