fix: use real totalCount from Subsquid instead of capped fetch limit

Add totalCount to the GraphQL query so transactionCount reflects the
true number of transfers in the period, not the 2000-item fetch cap.
This also fixes the average Ğ1/tx calculation.

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

src/services/DataService.ts

@@ -37,10 +37,9 @@ async function fetchLiveTransactions(periodDays: number): Promise<{
   totalCount: number;
   totalVolume: number;
 }> {
-  const rawTransfers = await fetchTransfers(periodDays);
+  const { transfers: rawTransfers, totalCount } = await fetchTransfers(periodDays);
   if (rawTransfers.length === 0) return { geolocated: [], totalCount: 0, totalVolume: 0 };
 
-  const totalCount  = rawTransfers.length;
   const totalVolume = rawTransfers.reduce((s, t) => s + t.amount, 0);
 
   // Carte SS58 courant → clé Duniter (= _id Cesium+)