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/composables/useLastViewedUpload.ts

@@ -15,3 +15,17 @@ export interface PendingUploadMedia {
 export function usePendingUploadMedia() {
   return useState<PendingUploadMedia | null>('pending-upload-media', () => null)
 }
+
+export interface UploadNavContext {
+  uploadId: string
+  fromPath: string | null
+  fromLabel: string | null
+}
+
+// Herkunft der Thread-Navigation (z. B. /user/<id>): beim Tile-Klick gesetzt
+// und von den Thread-Pfeilen für die Folgeseite weitergereicht. Gilt immer
+// nur für die in uploadId hinterlegte Seite — ein direkt geöffneter Thread
+// (Notification, Kommentar-Link, Reload) fällt auf die globale Reihenfolge
+export function useUploadNavContext() {
+  return useState<UploadNavContext | null>('upload-nav-context', () => null)
+}