fix(uploads): serve private previews through API and show batch cover status

packages/i18n/locales/en/admin.json

@@ -294,6 +294,11 @@
     "filter_withdrawn": "Withdrawn",
     "expand_batch": "Expand batch",
     "collapse_batch": "Collapse batch",
+    "batch_cover_present": "Cover attached",
+    "batch_cover_absent": "No cover",
+    "preview_http_error": "Could not load audio: HTTP {{status}}.",
+    "preview_decode_error": "The browser could not read the audio: check file access and format support.",
+    "preview_error": "Could not load audio. Check your connection and retry.",
     "col_file": "Track",
     "col_status": "Status",
     "col_size": "Size",