Optional product logos for tool icons in the customer and admin panels.

Put the official file here on the controller (e.g. /opt/nexpanel/public/images/tools/):

  <tool>.svg or <tool>.png (square, transparent background)

The panel uses it for "WordPress Manager" / "WP Toolkit" icons wherever it
exists, and falls back to the built-in line icon when it does not. Files here
are kept across controller updates.
