feat(frontend): add race details page with completed metrics

Implement race detail routing and UI with client-side pace calculation so completed race metrics are visible from the calendar flow.

Made-with: Cursor

frontend/src/pages/RacesPage.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useMemo, useState } from "react";
+import { Link } from "react-router-dom";
 import type { Race } from "../api";
 import { ApiError, getRaces } from "../api";
 import { formatDistance, formatRaceDate, getRaceStatusLabel, splitRacesByDate } from "../lib";
@@ -21,7 +22,11 @@ function RaceList(props: { title: string; races: Race[] }): JSX.Element {
           {races.map((race) => (
             <li key={race.id} className="race-card">
               <div className="race-card__main">
-                <p className="race-card__title">{race.title}</p>
+                <p className="race-card__title">
+                  <Link className="race-card__link" to={`/races/${race.id}`}>
+                    {race.title}
+                  </Link>
+                </p>
                 <p className="race-card__meta">
                   {formatRaceDate(race.date)} · {formatDistance(race.distanceKm)}
                 </p>