Add bianca suite support and fix security mirror URL

Adds the bianca suite to the packages website alongside aria, and fixes the security archive URL to point to the correct mirror.

Added bianca to suites and security_suites Added arch_bianca and ext_bianca definitions (amd64, arm64 / gz) Fixed security_ftpsite from non-existent security.elxr.dev to mirror.elxr.dev/elxr Added bianca => 'stable' to suite aliases Added bianca to all_suites and version_numbers (13.0) Set current_release to bianca Added all sections (contrib, non-free-firmware, community variants)