Offer the three proposed font groups in Themes

The theme menu now carries a fourth choice beside light/dark and the accent:
the font pairing. All three pairings are free for commercial use (SIL OFL),
have a Vietnamese subset, and are self-hosted — the landing still makes no
CDN request.

- styles/fonts.css: 22 @font-face blocks for Plus Jakarta Sans, Inter,
  JetBrains Mono, Fraunces, Be Vietnam Pro, Courier Prime and Space Mono,
  vietnamese/latin-ext/latin subsets only, under public/assets/fonts.
- styles/tokens.css: [data-fonts="studio|editorial|native"] sets --font,
  --font-heading and --mono. Studio (Plus Jakarta Sans + Inter + JetBrains
  Mono) is the default.
- theme/: FontSetId + FONT_SETS, persisted as rc.fonts, applied as
  <html data-fonts> next to data-theme and data-accent.
- TopBar and the landing nav both get the picker; on the landing the theme
  tool now opens a small popover (light/dark + font group) instead of
  toggling on click.
- landing.css: --lp-display/--lp-mono now resolve to the chosen group, so the
  picker retypes the whole page. Syne.woff2 goes with its @font-face.

docker/README.md

@@ -48,11 +48,15 @@ project (`@shopify/react-native-skia` is aliased to `src/engine/skiaShim.ts` in
 `cinemaShader` `colorUtils` `defaultRecipes` `exifWrite` `frameUtils` `jpegDpi`
 `paramDefs` `recipeShare` `skiaImage` `toneShader`.
 
-The landing page needs no CDN: `frontend/public/assets/Syne.woff2` is the
-bundled display face and `frontend/public/assets/samples/s*.jpg` are the six
-placeholder negatives the film strip, preset tester and QR card show (swap them
-for real graded stills whenever we have them). Its one foreign request is the
-QR image from `api.qrserver.com`, which degrades to an empty slot offline.
+The landing page needs no CDN: `frontend/public/assets/fonts/*.woff2` are the
+seven self-hosted faces behind the three font groups the Themes menu offers
+(Plus Jakarta Sans / Inter / JetBrains Mono, Fraunces / Be Vietnam Pro /
+Courier Prime, Be Vietnam Pro / Space Mono — all SIL OFL, pulled from Google
+Fonts, vietnamese + latin + latin-ext subsets), and
+`frontend/public/assets/samples/s*.jpg` are the six placeholder negatives the
+film strip, preset tester and QR card show (swap them for real graded stills
+whenever we have them). Its one foreign request is the QR image from
+`api.qrserver.com`, which degrades to an empty slot offline.
 
 When the app changes one of them, copy it back in — the renderer is only
 "parity" for as long as these stay in sync: