style(qa3): design-token foundation + safe polish/a11y fixes

- Add :root design tokens in _typography.css (was empty) — brand teal/orange,
  ink/text greys, radius + type scale + section rhythm. Visually neutral;
  new rules can reference var()s instead of scattered literals.
- a11y: visible :focus-visible ring on header nav + dropdown links (keyboard
  users had none).
- Fix synthesized faux-bold: .route-report h1 800 -> 700 (Inter loads 400-700).
- Testimonials column: overflow-y scroll -> auto (no permanent scrollbar gutter).
- Lightbox image radius 6px -> 8px (matches the site rounding scale).
- Consistent card affordance: homepage .news-card now lifts on hover like the
  news-hub / blog cards.
- Re-stamped cache-bust (v=1f64b22f).

Deferred (needs a brand decision): unifying the two primary oranges
(#FA7850 vs #F2762E) and the fuller literal->token migration.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

css/pages/_home.css

@@ -437,7 +437,7 @@
     gap: 24px;
     width: 846px;
     height: 800px;
-    overflow-y: scroll;
+    overflow-y: auto; /* was scroll — no permanent scrollbar gutter when content fits */
     padding-right: 15px;
 }
 .testimonials-columns::-webkit-scrollbar {