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/frontend/src/lib/components/header/header.svelte

@@ -172,7 +172,7 @@
 <!-- Flyout panel -->
 <div
   class={`fixed inset-y-0 left-0 z-50 w-80 max-w-[85vw] bg-card/95 backdrop-blur-xl shadow-2xl shadow-primary/20 border-r border-border/30 transform transition-transform duration-300 ease-in-out lg:hidden overflow-y-auto flex flex-col ${isMobileMenuOpen ? "translate-x-0" : "-translate-x-full"}`}
-  aria-hidden={!isMobileMenuOpen}
+  inert={!isMobileMenuOpen || undefined}
 >
   <!-- Panel header -->
   <div class="flex items-center px-5 h-16 shrink-0 border-b border-border/30">

packages/frontend/src/lib/services.ts

@@ -229,10 +229,10 @@ const ARTICLES_QUERY = gql`
       category
       featured
       author {
-        first_name
-        last_name
+        id
+        artist_name
+        slug
         avatar
-        description
       }
     }
   }
@@ -259,10 +259,10 @@ const ARTICLE_BY_SLUG_QUERY = gql`
       category
       featured
       author {
-        first_name
-        last_name
+        id
+        artist_name
+        slug
         avatar
-        description
       }
     }
   }
@@ -1387,8 +1387,9 @@ const ADMIN_LIST_ARTICLES_QUERY = gql`
       featured
       content
       author {
-        first_name
-        last_name
+        id
+        artist_name
+        slug
         avatar
       }
     }
@@ -1467,6 +1468,7 @@ const UPDATE_ARTICLE_MUTATION = gql`
     $excerpt: String
     $content: String
     $imageId: String
+    $authorId: String
     $tags: [String!]
     $category: String
     $featured: Boolean
@@ -1479,6 +1481,7 @@ const UPDATE_ARTICLE_MUTATION = gql`
       excerpt: $excerpt
       content: $content
       imageId: $imageId
+      authorId: $authorId
       tags: $tags
       category: $category
       featured: $featured
@@ -1498,6 +1501,7 @@ export async function updateArticle(input: {
   excerpt?: string;
   content?: string;
   imageId?: string;
+  authorId?: string | null;
   tags?: string[];
   category?: string;
   featured?: boolean;