feat: make archive mount writable and raise upload cap (REQ-178)

frontend/nginx.conf

@@ -2,9 +2,9 @@ server {
     listen 80;
     server_name _;
 
-    # A base model upload is a whole .pt checkpoint; the default 1 MB would
-    # reject every one of them.
-    client_max_body_size 512m;
+    # Uploads are multi-GB: whole .pt checkpoints and multi-GB videos; the
+    # default 1 MB would reject every one of them.
+    client_max_body_size 20g;
 
     root /usr/share/nginx/html;
     index index.html;