feat(race-day): add warm-up transponder check before a heat

Race Day gets a 1-3 minute warm-up per heat with a green check per
driver when their transponder is seen, countdown announcements
(sv/en), quick transponder fix from the panel, and a start warning
that still allows starting when someone is missing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/styles.css

@@ -4447,3 +4447,45 @@ select:focus {
   font-size: 0.86rem;
   color: var(--muted, inherit);
 }
+
+.warmup-clock {
+  font-size: 1.6rem;
+  font-variant-numeric: tabular-nums;
+  margin-right: 8px;
+}
+
+.warmup-table {
+  width: 100%;
+  border-collapse: collapse;
+}
+
+.warmup-table td {
+  padding: 8px 6px;
+  border-top: 1px solid var(--line);
+  vertical-align: middle;
+}
+
+.warmup-status {
+  width: 2.2em;
+  text-align: center;
+  font-size: 1.2rem;
+}
+
+.warmup-table tr.is-missing td {
+  background: color-mix(in srgb, var(--accent) 8%, transparent);
+}
+
+.warmup-fix {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+  justify-content: flex-end;
+}
+
+.warmup-fix input {
+  width: 10em;
+}
+
+#raceDayWarmup .panel-header .pill {
+  white-space: nowrap;
+}