feat: add shared @sexy.pivoine.art/types package and fix type safety across frontend/backend

- Create packages/types with shared TypeScript domain model interfaces (User, Video, Model, Article, Comment, Recording, etc.)
- Wire both frontend and backend packages to use @sexy.pivoine.art/types via workspace:*
- Update backend Pothos objectRef types to use shared interfaces instead of inline types
- Update frontend $lib/types.ts to re-export from shared package
- Fix all type errors introduced by more accurate nullable types (avatar/banner as string|null UUIDs, author nullable, events/device_info as object[])
- Add artist_name to comment user select in backend resolver
- Widen utility function signatures (getAssetUrl, getUserInitials, calcReadingTime) to accept null/undefined

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

packages/frontend/src/routes/magazine/+page.svelte

@@ -26,8 +26,8 @@
       .filter((article) => {
         const matchesSearch =
           article.title.toLowerCase().includes(searchQuery.toLowerCase()) ||
-          article.excerpt.toLowerCase().includes(searchQuery.toLowerCase()) ||
-          article.author.first_name.toLowerCase().includes(searchQuery.toLowerCase());
+          article.excerpt?.toLowerCase().includes(searchQuery.toLowerCase()) ||
+          article.author?.first_name?.toLowerCase().includes(searchQuery.toLowerCase());
         const matchesCategory = categoryFilter === "all" || article.category === categoryFilter;
         return matchesSearch && matchesCategory;
       })
@@ -189,12 +189,12 @@
             <div class="flex items-center justify-between">
               <div class="flex items-center gap-3">
                 <img
-                  src={getAssetUrl(featuredArticle.author.avatar, "mini")}
-                  alt={featuredArticle.author.first_name}
+                  src={getAssetUrl(featuredArticle.author?.avatar, "mini")}
+                  alt={featuredArticle.author?.first_name}
                   class="w-10 h-10 rounded-full object-cover"
                 />
                 <div>
-                  <p class="font-medium">{featuredArticle.author.first_name}</p>
+                  <p class="font-medium">{featuredArticle.author?.first_name}</p>
                   <div class="flex items-center gap-3 text-sm text-muted-foreground">
                     <span>{timeAgo.format(new Date(featuredArticle.publish_date))}</span>
                     <span>•</span>
@@ -273,7 +273,7 @@
 
             <!-- Tags -->
             <div class="flex flex-wrap gap-2 mb-4">
-              {#each article.tags.slice(0, 3) as tag (tag)}
+              {#each (article.tags ?? []).slice(0, 3) as tag (tag)}
                 <a
                   class="text-xs bg-primary/10 text-primary px-2 py-1 rounded-full"
                   href="/tags/{tag}"
@@ -287,12 +287,12 @@
             <div class="flex items-center justify-between">
               <div class="flex items-center gap-2">
                 <img
-                  src={getAssetUrl(article.author.avatar, "mini")}
-                  alt={article.author.first_name}
+                  src={getAssetUrl(article.author?.avatar, "mini")}
+                  alt={article.author?.first_name}
                   class="w-8 h-8 rounded-full object-cover"
                 />
                 <div>
-                  <p class="text-sm font-medium">{article.author.first_name}</p>
+                  <p class="text-sm font-medium">{article.author?.first_name}</p>
                   <div class="flex items-center gap-2 text-xs text-muted-foreground">
                     <span class="icon-[ri--calendar-line] w-4 h-4"></span>
                     {timeAgo.format(new Date(article.publish_date))}

packages/frontend/src/routes/magazine/[slug]/+page.svelte

@@ -139,6 +139,7 @@
         </div>
 
         <!-- Author Bio -->
+        {#if 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">
@@ -164,15 +165,13 @@
                     >
                       {data.article.author.website}
                     </a>
-                    <!-- <a href="https://{data.article.author.social.website}" class="text-primary hover:underline">
-                    {data.article.author.social.website}
-                  </a> -->
                   </div>
                 {/if}
               </div>
             </div>
           </CardContent>
         </Card>
+        {/if}
       </article>
 
       <!-- Sidebar -->