Add full app source

Adds the Flutter inventory app source, cleaned up for a shared repo:
generic package name, no hardcoded ERP endpoints (moved to gitignored
local config), no dead auth code, no debug logging of session data.

lib/models/famille_produit.dart

@@ -0,0 +1,31 @@
+class FamilleProduit {
+  int? id;
+  String? name;
+
+  FamilleProduit({this.id, this.name});
+
+  FamilleProduit.fromJson(Map<dynamic, dynamic> json) {
+    id = json['id'];
+    name = json['name'];
+  }
+
+  Map<dynamic, dynamic> toJson() {
+    final Map<dynamic, dynamic> data = {};
+    data['id'] = id;
+    data['name'] = name;
+    return data;
+  }
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is FamilleProduit &&
+          runtimeType == other.runtimeType &&
+          id == other.id;
+
+  @override
+  String toString() => name ?? 'Unknown';
+
+  @override
+  int get hashCode => id.hashCode;
+}