fix: kickoff time centered without 'Uhr', unified countdown badge, DevPanel close button

- Kickoff: centered "21:00" above flags (no 'Uhr' suffix)
- Countdown: always rendered as badge (was unstyled span for <60min)
- DevPanel: added close button (✕) in panel header for reliable closing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/MatchCard.module.css

@@ -77,12 +77,17 @@
   border: 1px solid rgba(75,183,248,0.15);
 }
 
-/* Kickoff badge in header row */
-.kickoffBadge {
-  font-size: 12px;
+/* Kickoff time — centered above flags */
+.kickoffRow {
+  text-align: center;
+  margin-bottom: 6px;
+}
+
+.kickoffTime {
+  font-size: 13px;
   font-weight: 700;
   color: var(--text-secondary);
-  letter-spacing: 0.02em;
+  letter-spacing: 0.05em;
 }
 
 .topRowSpacer {