Number entries on publish, delete media, read the cover

- drafts stay unnumbered, the number is handed out when an entry goes live
- DELETE /api/v1/media/:id and a delete control in the media library
- cover_media_id in the draft read, coverMediaId and coverUrl in the archive read

src/data/schema/posts.ts

@@ -24,7 +24,7 @@ export const posts = pgTable('post', {
 	id: uuid('id').primaryKey().defaultRandom(),
 	projectId: uuid('project_id').notNull().references(() => projects.id, { onDelete: 'cascade' }),
 	issueId: uuid('issue_id').references(() => issues.id, { onDelete: 'set null' }),
-	number: integer('number').notNull(),
+	number: integer('number'),
 	slug: text('slug').notNull(),
 	title: text('title').notNull(),
 	teaser: text('teaser'),