fix(embed): restore youtube thumbnails and file-row labels (#1148)

* fix(comment-content): render reason text as comment content

* fix(post-form): use native browser styling for flash tag select

Exclude the flash tag dropdown from themed post-form select styling so it
renders with the browser's default select appearance, matching the flag selector.

* fix(p2p-stats): show peer flags for DNS6 relay hostnames

Extract embedded IPv6 addresses from dns6 multiaddrs so geo lookup and country flags work for relay peers that publish IPv6 via DNS hostnames.

* fix(flags): hide geolocation-only selectors on /int/ and /sp/

Country-only boards auto-publish geographic location flags without
showing a flag dropdown, matching existing /bant/ behavior.

* fix(embed): restore youtube thumbnails and file-row labels

Restore thumbnail-first previews for YouTube embeds in post media and markdown hover.
Desktop posts show File with the thumbnail image URL and a youtube video type label.

* fix(embed): address youtube thumbnail review feedback

Translate the youtube video label, handle mobile/music YouTube hosts as standard YouTube URLs, keep affected mocks current, and cap default Vitest workers to reduce local CPU spikes.

src/components/embed/embed-utils.ts

@@ -1,3 +1,5 @@
+const STANDARD_YOUTUBE_HOSTS = new Set<string>(['youtube.com', 'www.youtube.com', 'm.youtube.com', 'music.youtube.com', 'youtu.be', 'www.youtu.be']);
+
 export const youtubeHosts = new Set<string>([
   'youtube.com',
   'www.youtube.com',
@@ -46,6 +48,35 @@ const canEmbedHosts = new Set<string>([
   ...spotifyHosts,
 ]);
 
+export const getYouTubeVideoId = (parsedUrl: URL): string | null => {
+  if (parsedUrl.searchParams.has('list') && !parsedUrl.searchParams.get('v') && !parsedUrl.host.includes('youtu.be') && !parsedUrl.pathname.includes('/shorts/')) {
+    return null;
+  }
+
+  const videoIdFromQuery = parsedUrl.searchParams.get('v');
+  if (videoIdFromQuery) {
+    return videoIdFromQuery;
+  }
+
+  if (parsedUrl.host.includes('youtu.be')) {
+    return parsedUrl.pathname.slice(1).split('/')[0] || null;
+  }
+
+  if (parsedUrl.pathname.includes('/shorts/')) {
+    return parsedUrl.pathname.split('/shorts/')[1]?.split('/')[0] || null;
+  }
+
+  const isInvidious = !STANDARD_YOUTUBE_HOSTS.has(parsedUrl.host) && (youtubeHosts.has(parsedUrl.host) || parsedUrl.host.startsWith('yt.'));
+  if (isInvidious) {
+    if (parsedUrl.pathname.startsWith('/watch')) {
+      return parsedUrl.searchParams.get('v');
+    }
+    return parsedUrl.pathname.split('/').filter(Boolean).pop() || null;
+  }
+
+  return null;
+};
+
 export const canEmbed = (parsedUrl: URL): boolean => {
   if (xHosts.has(parsedUrl.host)) {
     return Boolean(getXTweetId(parsedUrl));