feat: show country flag next to city names in top villes

Determine country from geoPoint coordinates using bounding boxes
for the main Ğ1 community countries (FR, BE, CH, ES, DE, IT, ...).
Display the emoji flag before each city name in the top villes panel.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/StatsPanel.tsx

@@ -1,5 +1,6 @@
 import { useRef } from 'react';
 import type { PeriodStats } from '../services/DataService';
+import { countryCodeToFlag } from '../services/adapters/CesiumAdapter';
 
 interface StatsPanelProps {
   stats: PeriodStats | null;
@@ -120,7 +121,9 @@ export function StatsPanel({ stats, loading, periodDays, source }: StatsPanelPro
             >
               <span className="text-base">{MEDALS[i]}</span>
               <div className="flex-1 min-w-0">
-                <p className="text-white text-sm font-medium truncate">{city.name}</p>
+                <p className="text-white text-sm font-medium truncate">
+                  {countryCodeToFlag(city.countryCode)}{city.countryCode ? ' ' : ''}{city.name}
+                </p>
                 <p className="text-[#6b7280] text-xs">{city.count} tx</p>
               </div>
               <span className="text-[#d4a843] text-sm font-mono shrink-0 flex items-center gap-1">