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/OddsCell.razor

@@ -60,7 +60,7 @@
         color: var(--m-c-ink-soft);
         transition: color 220ms ease;
     }
-    .m-odds.is-up .m-odds__delta { color: var(--m-c-accent); }
+    .m-odds.is-up .m-odds__delta { color: var(--m-c-positive); }
     .m-odds.is-down .m-odds__delta { color: var(--m-c-anomaly); }
     .m-odds.is-flat .m-odds__delta { color: var(--m-c-ink-soft); }