refactor: remove preview property from blog post schema and configuration

- Eliminated the optional `preview` field from the blog post schema and configuration to streamline data handling.
- Updated the blog post schema to utilize the default image directly from configuration, enhancing consistency in image representation.

src/content/config.ts

@@ -9,7 +9,6 @@ const blog = defineCollection({
 		description: z.string(),
 		draft: z.optional(z.boolean()),
 		lang: z.string(),
-		preview: z.optional(z.string()),
 		title: z.string(),
 	}),
 });

src/utils/schemas/blogPostSchema.ts

@@ -7,19 +7,18 @@ export type BlogPostSchemaParams = {
 	readonly description: string;
 	readonly isBasedOn?: string;
 	readonly lang: string;
-	readonly preview?: string;
 	readonly siteUrl: string;
 	readonly slug: string;
 	readonly title: string;
 };
 
-export default ({ siteUrl, slug, title, description, preview, datePublished, dateModified, lang, isBasedOn }: BlogPostSchemaParams): WithContext<BlogPosting> => ({
+export default ({ siteUrl, slug, title, description, datePublished, dateModified, lang, isBasedOn }: BlogPostSchemaParams): WithContext<BlogPosting> => ({
 	"@context": "https://schema.org",
 	"@type": "BlogPosting",
 	"url": new URL(`/blog/${slug}`, siteUrl).toString(),
 	"headline": title,
 	"description": description,
-	"image": new URL(preview ? preview : config.posts.defaultImage, siteUrl).toString(),
+	"image": new URL(config.posts.defaultImage, siteUrl).toString(),
 	"datePublished": datePublished,
 	"dateModified": dateModified,
 	"inLanguage": lang,