feat: enhance blog post and page schema with new properties

- Added optional `basedOn` field to blog post schema for better content attribution.
- Updated blog post markdown to include `basedOn` reference for improved context.
- Refactored page schema to replace deprecated website schema, enhancing structured data representation.
- Adjusted 404 and index pages to utilize the new page schema for consistency and SEO improvements.

src/content/config.ts

@@ -4,6 +4,7 @@ const blog = defineCollection({
 	type: "content",
 	schema: z.object({
 		author: z.string(),
+		basedOn: z.optional(z.string()),
 		dateModified: z.coerce.date(),
 		datePublished: z.coerce.date(),
 		description: z.string(),