Checkpoint: Ajout d'un tableau de bord détaillé avec statistiques avancées et graphiques.

Nouvelles fonctionnalités :
- Cartes de statistiques : Factures traitées, Montant total, Score moyen, Dernière activité
- Graphique en barres : Évolution des factures par semaine (30 derniers jours)
- Graphique circulaire : Top 10 fournisseurs avec pourcentages
- Liste détaillée : Tous les fournisseurs avec nombre de factures et montants
- Bouton "Voir les statistiques détaillées" pour afficher/masquer les graphiques
- Calculs automatiques : montant moyen par facture, score de qualité avec label (Excellent/Bon/Moyen/Faible)

Le dashboard utilise Recharts pour les visualisations et offre une vue complète de l'activité de traitement des factures.

server/db.ts

@@ -252,14 +252,97 @@ export async function searchInvoices(userId: number, query: string): Promise<Inv
 
 export async function getInvoiceStats(userId: number) {
   const db = await getDb();
-  if (!db) return { total: 0, completed: 0, processing: 0, error: 0 };
+  if (!db) return { 
+    total: 0, 
+    completed: 0, 
+    processing: 0, 
+    error: 0,
+    totalAmount: 0,
+    averageScore: 0,
+    lastActivity: null,
+    weeklyData: [],
+    topSuppliers: [],
+    suppliersList: []
+  };
   
   const allInvoices = await getInvoicesByUserId(userId);
+  
+  // Calculate basic stats
+  const completed = allInvoices.filter(i => i.status === "completed");
+  const totalAmount = completed.reduce((sum, inv) => sum + (Number(inv.totalAmount) || 0), 0);
+  const averageScore = completed.length > 0 
+    ? completed.reduce((sum, inv) => sum + (inv.qualityScore || 0), 0) / completed.length 
+    : 0;
+  
+  // Get last activity
+  const sortedByDate = [...allInvoices].sort((a, b) => 
+    new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime()
+  );
+  const lastActivity = sortedByDate[0]?.createdAt || null;
+  
+  // Calculate weekly data (last 30 days)
+  const now = new Date();
+  const thirtyDaysAgo = new Date(now.getTime() - 30 * 24 * 60 * 60 * 1000);
+  const weeklyMap = new Map<string, number>();
+  
+  allInvoices.forEach(inv => {
+    const date = new Date(inv.createdAt);
+    if (date >= thirtyDaysAgo) {
+      const weekStart = new Date(date);
+      weekStart.setDate(date.getDate() - date.getDay()); // Start of week
+      const weekKey = `${weekStart.getDate().toString().padStart(2, '0')}/${(weekStart.getMonth() + 1).toString().padStart(2, '0')}`;
+      weeklyMap.set(weekKey, (weeklyMap.get(weekKey) || 0) + 1);
+    }
+  });
+  
+  const weeklyData = Array.from(weeklyMap.entries())
+    .map(([week, count]) => ({ week, count }))
+    .sort((a, b) => {
+      const [dayA, monthA] = a.week.split('/').map(Number);
+      const [dayB, monthB] = b.week.split('/').map(Number);
+      return (monthA! * 100 + dayA!) - (monthB! * 100 + dayB!);
+    });
+  
+  // Calculate top suppliers
+  const supplierMap = new Map<string, { count: number; amount: number }>();
+  completed.forEach(inv => {
+    const supplier = inv.supplierName || 'Inconnu';
+    const current = supplierMap.get(supplier) || { count: 0, amount: 0 };
+    supplierMap.set(supplier, {
+      count: current.count + 1,
+      amount: current.amount + (Number(inv.totalAmount) || 0)
+    });
+  });
+  
+  const topSuppliers = Array.from(supplierMap.entries())
+    .map(([name, data]) => ({
+      name,
+      count: data.count,
+      amount: data.amount,
+      percentage: completed.length > 0 ? (data.count / completed.length * 100) : 0
+    }))
+    .sort((a, b) => b.count - a.count)
+    .slice(0, 10);
+  
+  const suppliersList = Array.from(supplierMap.entries())
+    .map(([name, data]) => ({
+      name,
+      count: data.count,
+      amount: data.amount
+    }))
+    .sort((a, b) => b.count - a.count);
+  
   return {
     total: allInvoices.length,
-    completed: allInvoices.filter(i => i.status === "completed").length,
+    completed: completed.length,
     processing: allInvoices.filter(i => i.status === "processing").length,
     error: allInvoices.filter(i => i.status === "error").length,
+    totalAmount,
+    averageScore: Math.round(averageScore),
+    lastActivity,
+    weeklyData,
+    topSuppliers,
+    suppliersList
   };
 }