refactor: align article author with VideoModel, streamline selects, fix flyout inert

- Remove ArticleAuthor type; article.author now reuses VideoModel (id, artist_name, slug, avatar)
- updateArticle accepts authorId; author selectable in admin article edit page
- Article edit: single Select with bind:value + $derived selectedAuthor display
- Video edit: replace pill toggles with Select type="multiple" bind:value for models
- Video table: replace inline badge spans with Badge component
- Magazine: display artist_name throughout, author bio links to model profile
- Fix flyout aria-hidden warning: replace with inert attribute

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/backend/src/graphql/resolvers/articles.ts

@@ -9,10 +9,10 @@ async function enrichArticle(db: any, article: any) {
   if (article.author) {
     const authorUser = await db
       .select({
-        first_name: users.first_name,
-        last_name: users.last_name,
+        id: users.id,
+        artist_name: users.artist_name,
+        slug: users.slug,
         avatar: users.avatar,
-        description: users.description,
       })
       .from(users)
       .where(eq(users.id, article.author))
@@ -132,6 +132,7 @@ builder.mutationField("updateArticle", (t) =>
       excerpt: t.arg.string(),
       content: t.arg.string(),
       imageId: t.arg.string(),
+      authorId: t.arg.string(),
       tags: t.arg.stringList(),
       category: t.arg.string(),
       featured: t.arg.boolean(),
@@ -145,6 +146,7 @@ builder.mutationField("updateArticle", (t) =>
       if (args.excerpt !== undefined) updates.excerpt = args.excerpt;
       if (args.content !== undefined) updates.content = args.content;
       if (args.imageId !== undefined) updates.image = args.imageId;
+      if (args.authorId !== undefined) updates.author = args.authorId;
       if (args.tags !== undefined && args.tags !== null) updates.tags = args.tags;
       if (args.category !== undefined) updates.category = args.category;
       if (args.featured !== undefined && args.featured !== null) updates.featured = args.featured;