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.

src/pdf/templates/northline/variant.ts

@@ -5,7 +5,7 @@ import type { GapRange } from "../neutral/variant";
 /**
  * Gotham (commercial) is drawn with Montserrat, which runs about 4% wider at the same size. Every Gotham-derived
  * size is multiplied by this when a token is defined, so the substitute takes the width the design has. A real
- * Gotham imported over the licensed name would need these tokens at factor 1.
+ * Gotham imported over the licensed name takes the design size back: each such token carries it as `ownFont.size`.
  */
 export const GOTHAM_SIZE = 0.96;
 const round2 = (n: number) => Math.round(n * 100) / 100;