Add font import for Now, Gotham and Open Sauce One overrides; package fonts for Void

Font import:
- Migration M6 adds user_fonts; files are stored content-addressed under
  the local data dir. New Rust commands inspect, import, list, read and
  remove fonts, refusing WOFF2, collections, variable fonts and
  restricted fsType, and unpacking WOFF1 to plain sfnt.
- Imported fonts register in the render worker as user:<Face> families
  with an italic alias, and are pinned in the frozen render prefs so
  issued invoices can still re-render. Fonts referenced by issued
  invoices are hidden, never deleted.
- Size and tracking compensations tuned for the substitutes apply only
  while the face is not overridden; default output and fingerprint
  goldens are unchanged.
- Settings gets a Fonts section with a licence acknowledgement.

Void packaging:
- Install fonts to /usr/share/fonts/voiced with per-family OFL licences,
  set font_dirs, and add INSTALL/REMOVE scripts that run fc-cache.
  xbps-create carries both scripts (verified in a void-glibc container).
- Fix xbps-create dependency specs in build-xbps.sh.

packaging/void/REMOVE

@@ -0,0 +1,14 @@
+#!/bin/sh
+# xbps action script for 'voiced': $1 = action, $2 = pkgname, $3 = version.
+#
+# Refreshes the fontconfig cache after the bundled fonts are removed, so stale
+# entries for /usr/share/fonts/voiced do not linger.
+# Never fails the transaction: a missing fc-cache or a cache error is ignored.
+case "$1" in
+post)
+    if command -v fc-cache >/dev/null 2>&1; then
+        fc-cache -f /usr/share/fonts/voiced >/dev/null 2>&1 || :
+    fi
+    ;;
+esac
+exit 0