Add functionality to manage and track customer credit notes

Introduces the "Avoirs" feature, including database schema, API endpoints for CRUD operations, and frontend components for viewing and managing credit notes.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 9fcf4b21-eb0c-4e53-a567-e2ce4a6ad869
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/9fcf4b21-eb0c-4e53-a567-e2ce4a6ad869/0C3uBiZ

client/src/components/Sidebar.tsx

@@ -32,7 +32,8 @@ import {
   Settings,
   Wrench,
   FileUp,
-  Send
+  Send,
+  Receipt
 } from "lucide-react";
 
 export default function Sidebar() {
@@ -284,6 +285,12 @@ export default function Sidebar() {
       icon: Wrench, 
       roles: ["admin", "directeur", "manager", "employee"] 
     },
+    { 
+      path: "/avoirs", 
+      label: "Avoirs", 
+      icon: Receipt, 
+      roles: ["admin", "directeur", "manager"] 
+    },
   ];
 
   const adminItems = [