Add auto-import schemes in `Config`

[rikettsie]

The config.json should support an auto_import_schemes key, used by the receive command to auto-import the received blob, also associating them to predefined rings if these have been specified in a scheme.

The structure of the auto_import_schemes is for example:

[
  {
    "prefix_path": "/home/peerx/Documents/articles/",
    "rings": ["papers"]
  },
  {
    "prefix_path": "/home/peerx/Pictures/Summer2026/",
    "rings": ["family", "summer"]
  }
]

When the receive command finished successfully, it should:

• verify if the destination path of the current download includes any prefix_path, if so:
  • it should import the newly received blob in the registry;
  • associate the blob with rings specified in the rings key.