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.

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

app/components/UploadTile.vue

@@ -120,14 +120,14 @@ async function openUpload(e: MouseEvent) {
 
   // Die eigentliche Navigation macht der NuxtLink bereits beim Klick —
   // dieser Push ist nur noch Fallback und bei gleicher Route ein No-Op
-  await router.push(`/thread/${props.upload.id}`)
+  await router.push(`/t/${props.upload.id}`)
   navigating.value = false
 }
 </script>
 
 <template>
   <NuxtLink
-    :to="`/thread/${upload.id}`"
+    :to="`/t/${upload.id}`"
     class="upload-tile group block"
     :class="[spanClass, navigating ? 'opacity-80' : '']"
     @click.capture="captureClick"