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/render/render.worker.ts

@@ -3,6 +3,7 @@ import { installStreamAsyncIterator } from "../../lib/streamPolyfill";
 import { initBrowserRendering } from "./browserInit";
 import { runAssembleJob } from "./assembleJob";
 import { renderInvoicePdf } from "./invoice";
+import { registerJobFonts } from "./userFontJob";
 import type { WorkerMessage, WorkerRequest } from "./jobs";
 
 interface WorkerScope {
@@ -44,6 +45,7 @@ scope.onmessage = async (event) => {
   const { job } = request;
   try {
     await started.catch(() => initBrowserRendering());
+    await registerJobFonts(job.prefs, job.userFonts);
     const t0 = performance.now();
     const out = await renderInvoicePdf({ model: job.model, prefs: job.prefs });
     const ms = Math.round(performance.now() - t0);