Keep thread navigation within the originating upload list

Record where an upload was opened from in a new useUploadNavContext
state. When a tile is clicked on a user profile, the thread page passes
that context to the upload detail API, which scopes the newer/older
neighbors to that user's uploads. Arrow clicks reseed the context for
the next thread, so the chain stays within the source list without a
URL parameter. Threads opened directly (notification, reload) fall back
to the global order. The breadcrumb reads the same context and shows
the profile path for profile-originated threads, now including the
thread id in the final crumb.

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

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

app/components/UploadTile.vue

@@ -37,8 +37,13 @@ const canPlaceholder = computed(() => {
 
 const indicator = useLoadingIndicator()
 const router = useRouter()
+const route = useRoute()
 const navigating = ref(false)
 
+// Herkunft im State merken (kein URL-Param): /user/<id> scopt Thread-Pfeile
+// und Breadcrumbs auf die Uploads dieses Nutzers
+const navContext = useUploadNavContext()
+
 const spanClass = computed(() => {
   if (uniform.value) return ''
   const count = props.upload.commentCount ?? 0
@@ -81,6 +86,11 @@ async function openUpload(e: MouseEvent) {
     url: props.upload.url,
     thumbUrl: props.upload.thumbUrl ?? null,
   }
+  navContext.value = {
+    uploadId: props.upload.id,
+    fromPath: /^\/user\/\d+$/.test(route.path) ? route.path : null,
+    fromLabel: props.upload.userName ?? null,
+  }
 
   try {
     const threadFetch = $fetch(`/api/uploads/${props.upload.id}`)