feat(rotation): per-device image-selection preferences

Adds two settings exposed in the PWA frame-settings sheet:

- rotationMode (enum: random | least_recently_shown | oldest_upload |
  newest_upload). Default oldest_upload preserves the legacy
  hard-coded sort, so existing devices behave identically until the
  user changes it.
- prioritizeNeverShown (bool). When set, the candidate set is narrowed
  to never-shown images first (if any exist) before the mode runs —
  useful for "burn through new uploads before re-shuffling the catalog."

RotationService pipeline:
  1. Pull approved/ready pool.
  2. Drop the last `uniquenessWindow` served (existing).
  3. If prioritizeNeverShown AND any candidates have never been served,
     narrow to those.
  4. Apply the selection mode.

Backend: enum, entity columns + accessors, migration, serializer,
PATCH validator. Frontend: types, stores, settings sheet section
(dropdown + checkbox), test fixtures, save-flow test.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Controller/DeviceApiController.php

@@ -10,6 +10,7 @@ use App\Entity\RenderedAsset;
 use App\Entity\User;
 use App\Enum\Orientation;
 use App\Enum\RenderStatus;
+use App\Enum\RotationMode;
 use App\Service\DeviceSerializer;
 use App\Service\MercurePublisher;
 use Doctrine\ORM\EntityManagerInterface;
@@ -119,6 +120,18 @@ class DeviceApiController extends AbstractController
             $device->setUniquenessWindow(max(1, (int) $body['uniquenessWindow']));
         }
 
+        if (isset($body['rotationMode'])) {
+            $mode = RotationMode::tryFrom((string) $body['rotationMode']);
+            if (!$mode) {
+                return $this->json(['error' => 'Invalid rotation mode'], Response::HTTP_UNPROCESSABLE_ENTITY);
+            }
+            $device->setRotationMode($mode);
+        }
+
+        if (array_key_exists('prioritizeNeverShown', $body)) {
+            $device->setPrioritizeNeverShown((bool) $body['prioritizeNeverShown']);
+        }
+
         $em->flush();
         $payload = $this->serializer->serialize($device);
         $this->mercure->publishDevice((int) $device->getId(), $payload);