feat(server): track upload status via manifest and /status API

- Persist per-box file metadata in a .warpbox.json manifest, including IDs and status fields (pending/uploading/complete/failed)
- Add GET /box/:id/status to return current file states for clients polling upload progress
- Update upload handling to mark failures and completion in the manifest and decorate responses
- Add CSS states for loading/failed files and disable interactions for unavailable itemsfeat(server): track upload status via manifest and /status API

- Persist per-box file metadata in a .warpbox.json manifest, including IDs and status fields (pending/uploading/complete/failed)
- Add GET /box/:id/status to return current file states for clients polling upload progress
- Update upload handling to mark failures and completion in the manifest and decorate responses
- Add CSS states for loading/failed files and disable interactions for unavailable items

static/css/upload.css

@@ -204,6 +204,11 @@
     background: #f7f7f7;
 }
 
+.upload-file-row.is-uploading,
+.upload-file-row.is-processing {
+    animation: upload-row-loading 900ms steps(2, end) infinite;
+}
+
 .upload-file-icon {
     grid-row: 1 / 3;
     width: 16px;
@@ -269,6 +274,16 @@
     background: #800000;
 }
 
+@keyframes upload-row-loading {
+    0% {
+        background-color: #ffffff;
+    }
+
+    100% {
+        background-color: #e6e6e6;
+    }
+}
+
 .upload-actions {
     display: flex;
     justify-content: flex-end;