Fix remote asset list not showing newly uploaded images (#156)

After upload, assets were not yet in the manifest-backed list. This change:

- Add manifest revision (hash of URLs) to the list API so the client can detect updates
- After upload, poll until uploaded URLs appear in the manifest instead of a single re-fetch
- Show processing state and optional "refresh available" prompt; support background sync on focus/visibility
- Move upload/processing messages to YAML translations (i18n)

Closes #86.

Author: schramm-joboo

src/RemoteContentAssets/Presentation/Controller/RemoteAssetsController.php

@@ -68,7 +68,10 @@ public function list(string $projectId): JsonResponse
             $project->remoteContentAssetsManifestUrls
         );
 
-        return $this->json(['urls' => $urls]);
+        return $this->json([
+            'urls'     => $urls,
+            'revision' => $this->buildUrlsRevision($urls),
+        ]);
     }
 
     /**
@@ -164,4 +167,14 @@ public function upload(string $projectId, Request $request): JsonResponse
             return $this->json(['error' => 'Upload failed: ' . $e->getMessage()], Response::HTTP_INTERNAL_SERVER_ERROR);
         }
     }
+
+    /**
+     * @param list<string> $urls
+     */
+    private function buildUrlsRevision(array $urls): string
+    {
+        sort($urls, SORT_STRING);
+
+        return hash('sha256', implode("\n", $urls));
+    }
 }