Scrollable upload grid and bulk rating for the pending backlog

Upload board:
- the tile grid no longer re-sorts itself as files finish (that reshuffled
  the list under the cursor); it keeps insertion order, uses auto-fill tiles
  of ~150px so they hold a readable size, scrolls inside a 60vh area and no
  longer chains the page scroll (overscroll-contain);
- the files currently in flight are pinned in a small live strip above the
  grid (name, percent, bar) so progress stays visible while the grid is
  scrolled with hundreds of tiles.

Bulk rating: a 'bulk rate' button in the Pending & Unmatched header opens a
large modal with Safe/Questionable/Explicit pills, a tickable thumbnail grid
(Select all / Clear) and one confirm that moves every selected upload into
the library with that rating. Backed by POST /api/uploads/resolve-bulk/
(temp_ids + rating, own rows only): each staged file is resolved as a custom
entry (keeps its staged tags/notes), and already-completed or foreign ids are
reported per entry instead of failing the whole batch. Built for the
358-file backlog.

Tests: 4 bulk-resolve tests (resolution with the rating, input validation,
foreign ids untouched, mixed completed+pending) — full backend suite 53
green. Verified live end to end: staged a file, bulk-resolved it as 'q', saw
J-96 created with that rating, then removed the item, temp row and test
token.

backend/apps/library/uploads.py

@@ -17,6 +17,7 @@ from urllib.parse import urlparse
 from django.conf import settings
 from django.contrib.auth import get_user_model
 from django.core import signing
+from django.core.exceptions import ValidationError
 from django.http import Http404
 from django.utils import timezone
 from rest_framework import mixins, status, viewsets
@@ -328,6 +329,64 @@ class TempUploadViewSet(
         temp.refresh_from_db()
         return Response(self.get_serializer(temp).data)
 
+    @action(detail=False, methods=["post"], url_path="resolve-bulk")
+    def resolve_bulk(self, request):
+        """Move many staged uploads into the library with one rating.
+
+        The upload board's bulk tool: pick a rating, tick pending files, and
+        they are all resolved as custom entries (their staged tags/notes are
+        kept). Own rows only, like the rest of the viewset.
+        """
+        ids = request.data.get("temp_ids")
+        if not isinstance(ids, list) or not ids:
+            return Response(
+                {"detail": "temp_ids must be a non-empty list."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+        rating = str(request.data.get("rating") or "").strip()
+        if rating not in {"s", "q", "e"}:
+            return Response(
+                {"detail": "rating must be one of s, q or e."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        try:
+            queryset = self.get_queryset().filter(
+                pk__in=[str(value) for value in ids]
+            )
+        except (ValidationError, ValueError):
+            return Response(
+                {"detail": "One or more ids are not valid upload ids."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        resolved: list[str] = []
+        errors: list[dict[str, str]] = []
+        for temp in queryset:
+            if temp.status == TempUpload.STATUS_COMPLETED:
+                errors.append(
+                    {"temp_id": str(temp.id), "error": "already in the library"}
+                )
+                continue
+            temp.custom_rating = rating
+            temp.resolution = TempUpload.RESOLUTION_CUSTOM
+            temp.save(update_fields=["custom_rating", "resolution", "updated_at"])
+            try:
+                complete_temp_upload(temp)
+            except Exception as exc:  # noqa: BLE001 - report per-file failures
+                logger.exception("Could not complete staged upload %s", temp.id)
+                temp.status = TempUpload.STATUS_ERROR
+                temp.save(update_fields=["status", "updated_at"])
+                errors.append({"temp_id": str(temp.id), "error": str(exc)})
+                continue
+            resolved.append(str(temp.id))
+
+        found = {str(temp.id) for temp in queryset}
+        for value in sorted({str(value) for value in ids} - found):
+            errors.append({"temp_id": value, "error": "not found"})
+
+        return Response({"resolved": resolved, "errors": errors})
+
     def perform_destroy(self, instance):
         if instance.file:
             instance.file.delete(save=False)