feat(ui): Velocity rollout — page polish + lime-as-text contrast fixes

Roll the re-skin across the remaining surfaces and fix the readability
regressions the lime accent introduced (lime works as a fill/border but is
unreadable as text on light):

- --m-c-rule is now a soft divider, so page panels/tables get tidy outlines
  instead of a mess of black hairlines; the brutalist weight stays on cards,
  nav, sections and inputs (which reference ink directly).
- New --m-c-warning (amber) for medium severity, keeping the low→medium→high
  gradient legible; applied to SeverityBadge, AnomalyCard, feed stat.
- Interactive/link/highlight text (Home CTA + links, Journal/Backtest/Compare
  buttons, KPI + evidence values) moved off lime to the readable --m-c-info
  blue; Home first-run CTA is now a filled-lime brutalist button; odds-up
  delta → positive green; rate arrow → neutral.
- Results winner colours → tokens (positive / info) + Velocity-aligned tints.

CSS-only — build clean, all 568 tests green.

src/Marathon.UI/Components/AnomalyCard.razor

@@ -77,7 +77,7 @@
         outline-offset: 2px;
     }
     .m-anomaly-card--high   { border-left-color: var(--m-c-anomaly); }
-    .m-anomaly-card--medium { border-left-color: var(--m-c-accent); }
+    .m-anomaly-card--medium { border-left-color: var(--m-c-warning); }
     .m-anomaly-card--low    { border-left-color: var(--m-c-ink-soft); }
 
     .m-anomaly-card__head {
@@ -132,7 +132,7 @@
         color: var(--m-c-ink-soft);
         font-size: 0.875rem;
     }
-    .m-anomaly-card__rate-arrow { color: var(--m-c-accent); font-size: 0.875rem; }
+    .m-anomaly-card__rate-arrow { color: var(--m-c-ink-soft); font-size: 0.875rem; }
     .m-anomaly-card__rate-post {
         color: var(--m-c-ink);
         font-weight: 600;