feat(ui): add used-by, a dependency map and a redesigned overview

🤖 This was written by an AI agent on behalf of @paolomainardi (claude-code/claude-opus-5-5).

Reworks the inventory pages: shows which projects bring in each package, adds a dependency map and redesigns the overview.

• Used by on the Packages and Security findings tables and in the assessment dialog: the Drupal project, extension or root package behind each Composer and npm package, with a filter.
• Dependency map tab: an interactive WebGL graph of the latest snapshot, built with the module's own code and no third-party libraries. Selecting a package shows the chains that bring it in; "Needs attention" keeps only packages with open findings. Without JavaScript or WebGL2 the tab links to the tables.
• Registry links for public packages (npmjs.com, Packagist, drupal.org), following the repository each package comes from; private packages get none.
• Overview redesign: page actions, a status card with explicit states (open findings, known exploited, unchecked or failed checks, partial results), a freshness row, and an ecosystem band that says when advisories have not been checked.
• Readability: thousands separators, bold numbers, tag chips, natural name wrapping and text alternatives for graphics.
• Docs and screenshots refreshed.

Checked in Claro, Gin 4 and Gin 5, light and dark. The map was validated on a 4,500-package site and a synthetic 5,000-package graph.

Includes !19 (closed), !20 (closed) and !21 (closed).

Follow-up to #3629895