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/base/_typography.css

@@ -0,0 +1,50 @@
+/* ==========================================================================
+   Design tokens
+   --------------------------------------------------------------------------
+   Single source of truth for values previously hard-coded as literals across
+   the stylesheets (e.g. #2D738C ~98×, #101828 ~103×). New/refactored rules
+   should reference these instead of raw hex. Values match the existing
+   dominant usages, so introducing this file is visually neutral — migrating
+   older literals to var() can happen incrementally.
+   ========================================================================== */
+:root {
+  /* Brand — teal */
+  --teal:        #2D738C;
+  --teal-600:    #255E73;   /* button hover */
+  --teal-800:    #153C4E;   /* deep accents */
+
+  /* Brand — orange.  NOTE: the site currently ships two primary oranges:
+     --orange (event pages / logo family) and --orange-cta (homepage buttons).
+     They read as slightly different brands side by side; unify on one once the
+     canonical value is confirmed. */
+  --orange:      #F2762E;
+  --orange-600:  #E85D2A;
+  --orange-cta:  #FA7850;
+  --orange-text: #B4531A;   /* AA-safe orange for text on white */
+
+  /* Ink / text */
+  --ink:         #101828;
+  --text:        #344054;
+  --muted:       #475467;
+  --muted-2:     #667085;   /* smallest muted text that still meets AA on white */
+
+  /* Surfaces / lines */
+  --bg:          #F9FAFB;
+  --line:        #EAECF0;
+  --line-2:      #E4E7EC;
+
+  /* Radius scale */
+  --r-sm:  8px;
+  --r-md:  12px;
+  --r-lg:  16px;
+  --r-pill: 999px;
+
+  /* Type scale (available for future heading normalisation) */
+  --fs-h1: 60px;
+  --fs-h2: 36px;
+  --fs-h3: 22px;
+  --fs-body: 16px;
+
+  /* Section vertical rhythm */
+  --space-section: 112px;
+}