Shorten thread route from /thread to /t

All internal links (tiles, prev/next nav, comments, notifications,
breadcrumb, dropzone route check) point to /t/<id>. A global route
middleware permanently redirects old /thread/<id> URLs including
query string and comment anchor.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/components/CommentsSidebar.vue

@@ -47,7 +47,7 @@ const mergedComments = computed(() => {
       <NuxtLink
         v-for="comment in mergedComments"
         :key="comment.id"
-        :to="`/thread/${comment.uploadId}#comment-${comment.id}`"
+        :to="`/t/${comment.uploadId}#comment-${comment.id}`"
         class="block rounded-md border border-sidebar-border/60 bg-sidebar px-3 py-2.5 text-sm transition-colors hover:border-sidebar-border hover:bg-sidebar-accent"
       >
         <div class="flex items-center gap-2 text-xs text-muted-foreground">