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/routes/magazine/[slug]/+page.svelte

@@ -141,32 +141,21 @@
 
         <!-- Author Bio -->
         {#if data.article.author}
+          {@const author = data.article.author}
           <Card class="p-0 bg-gradient-to-r from-card/50 to-card">
             <CardContent class="p-6">
               <div class="flex items-start gap-4">
                 <img
-                  src={getAssetUrl(data.article.author.avatar, "mini")}
-                  alt={data.article.author.first_name}
+                  src={getAssetUrl(author.avatar, "mini")}
+                  alt={author.artist_name}
                   class="w-16 h-16 rounded-full object-cover ring-2 ring-primary/20"
                 />
                 <div class="flex-1">
-                  <h3 class="font-semibold text-lg mb-2">
-                    About {data.article.author.first_name}
-                  </h3>
-                  {#if data.article.author.description}
-                    <p class="text-muted-foreground mb-4">
-                      {data.article.author.description}
-                    </p>
-                  {/if}
-                  {#if data.article.author.website}
-                    <div class="flex gap-4 text-sm">
-                      <a
-                        href={"https://" + data.article.author.website}
-                        class="text-primary hover:underline"
-                      >
-                        {data.article.author.website}
-                      </a>
-                    </div>
+                  <h3 class="font-semibold text-lg mb-2">About {author.artist_name}</h3>
+                  {#if author.slug}
+                    <a href="/models/{author.slug}" class="text-sm text-primary hover:underline">
+                      View profile
+                    </a>
                   {/if}
                 </div>
               </div>