feat: related content and featured cross-content sidebar widgets

- Add excludeId arg to videos and articles GraphQL resolvers
- Add excludeId + featured params to getVideos/getArticles services
- Video page: fetch related videos by tag + featured article in parallel
- Article page: fetch related articles by category + featured video in parallel
- Implement sidebar widgets with thumbnails, metadata, hover interactions
- Add videos.related and magazine.related i18n keys
- Seed dummy articles (spotlight, interview, psychology) and videos with
  overlapping tags for testing related content

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

packages/frontend/src/routes/videos/[slug]/+page.server.ts

@@ -1,18 +1,25 @@
 import { error } from "@sveltejs/kit";
-import { getCommentsForVideo, getVideoBySlug, getVideoLikeStatus } from "$lib/services.js";
+import {
+  getCommentsForVideo,
+  getVideoBySlug,
+  getVideoLikeStatus,
+  getVideos,
+  getArticles,
+} from "$lib/services.js";
 
 export async function load({ fetch, params, locals }) {
   const video = await getVideoBySlug(params.slug, fetch);
-  const comments = await getCommentsForVideo(video.id, fetch);
 
-  let likeStatus = { liked: false };
-  if (locals.authStatus.authenticated) {
-    try {
-      likeStatus = await getVideoLikeStatus(video.id, fetch);
-    } catch (error) {
-      console.error("Failed to get like status:", error);
-    }
-  }
+  const [comments, likeStatus, relatedVideos, featuredArticle] = await Promise.all([
+    getCommentsForVideo(video.id, fetch),
+    locals.authStatus.authenticated
+      ? getVideoLikeStatus(video.id, fetch).catch(() => ({ liked: false }))
+      : Promise.resolve({ liked: false }),
+    video.tags?.length
+      ? getVideos({ tag: video.tags[0], excludeId: video.id, limit: 5 }, fetch)
+      : Promise.resolve({ items: [], total: 0 }),
+    getArticles({ featured: true, limit: 1 }, fetch),
+  ]);
 
   try {
     return {
@@ -20,6 +27,8 @@ export async function load({ fetch, params, locals }) {
       comments,
       authStatus: locals.authStatus,
       likeStatus,
+      relatedVideos: relatedVideos.items,
+      featuredArticle: featuredArticle.items[0] ?? null,
     };
   } catch {
     error(404, "Video not found");