Unpaginate staged uploads and make big upload batches visible

The upload board partitions /api/uploads/ into Pending / Visual similarity /
Auto-uploaded, but the endpoint was paginated at 48 — a 69-file batch
silently lost 21 entries, and the similarity sweep (which reads the same
list back after uploading) only ever saw the first page. The staged-upload
list is now unpaginated: it is a transient per-user set, still limited to
the caller's rows and the uploader role. The page takes a plain array.

Watching progress with dozens of files was also poor:
- the queue uploads three files at a time instead of strictly one at a time;
- the Uploads section now shows a batch bar and 'n/m uploaded · x%' next to
  the count, so the overall progress never scrolls out of sight;
- entries are ordered active-first (uploading, queued, failed, done) so the
  file being uploaded is always at the top of the grid;
- tiles are larger (4 columns at lg instead of 5);
- the header reads 'Uploading n/m…' and 'Checking n file(s) against IQDB…'
  instead of a bare spinner.

Tests: staged-upload list unpaginated past 48, per-user, uploader-only
(3 new; full suite 49 green). Live-checked the bare-array response.

backend/apps/library/uploads.py

@@ -150,6 +150,9 @@ class TempUploadViewSet(
     serializer_class = TempUploadSerializer
     permission_classes = [CanUpload]
     parser_classes = [MultiPartParser, FormParser, JSONParser]
+    # Unpaginated: the board shows every staged upload (69-file batches were
+    # silently cut to the API's 48-item page).
+    pagination_class = None
     http_method_names = ["get", "post", "delete", "head", "options"]
 
     def get_queryset(self):