Add source files and streaming backup restore instructions

BACKUP_RESTORE.md

@@ -24,4 +24,4 @@ their original relative paths. Source code is already available as regular files
 
 The uploader uses `hf-mirror.com` for Git and LFS metadata. LFS payloads use the
 storage URLs returned by that service, as in a normal Git LFS transfer. It keeps
-only one archive volume in memory, plus small Git metadata and progress files.
+at most 16 archive volumes in memory (1 GiB total), plus small Git metadata and progress files.

backup-manifest.json

@@ -32,9 +32,14 @@
       "path": "backup/parts/radir-data.tar.zst.part-000003",
       "sha256": "68dfecc1d3b87fbc3259c9cae66118433b68eddbfb1fb932de77a657d7cc6273",
       "size": 67108864
+    },
+    {
+      "path": "backup/parts/radir-data.tar.zst.part-000004",
+      "sha256": "46e61f9b5c56636ea82733cf0e2a5db026aa2c56ff2fd0e6a159e145c527d748",
+      "size": 67108864
     }
   ],
-  "compressed_bytes": 268435456,
+  "compressed_bytes": 335544320,
   "archive_sha256": null,
   "restore": "python3 restore_backup.py",
   "source_files_unchanged": true

backup/parts/radir-data.tar.zst.part-000004

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:46e61f9b5c56636ea82733cf0e2a5db026aa2c56ff2fd0e6a159e145c527d748
+size 67108864